Remove unnecessary type conversions + added make command to do the same

[DhruvilK7]

unconvert indicates the following type conversions as unnecessary:

os/src/github.com/roaring/BitSliceIndexing/bsi.go:151:14: unnecessary conversion
os/src/github.com/roaring/BitSliceIndexing/bsi.go:770:31: unnecessary conversion
os/src/github.com/roaring/arraycontainer.go:996:14: unnecessary conversion
os/src/github.com/roaring/bitmapcontainer.go:1173:15: unnecessary conversion
os/src/github.com/roaring/bitmapcontainer.go:1195:15: unnecessary conversion
os/src/github.com/roaring/bitmapcontainer.go:1232:15: unnecessary conversion
os/src/github.com/roaring/bitmapcontainer_test.go:55:43: unnecessary conversion
os/src/github.com/roaring/ctz_test.go:108:29: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:202:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:207:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:212:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:218:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:232:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:235:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:242:17: unnecessary conversion
os/src/github.com/roaring/fastaggregation_test.go:251:17: unnecessary conversion
os/src/github.com/roaring/parallel.go:373:24: unnecessary conversion
os/src/github.com/roaring/parallel.go:375:19: unnecessary conversion
os/src/github.com/roaring/parallel.go:378:19: unnecessary conversion
os/src/github.com/roaring/parallel.go:381:31: unnecessary conversion
os/src/github.com/roaring/parallel.go:388:84: unnecessary conversion
os/src/github.com/roaring/parallel.go:389:51: unnecessary conversion
os/src/github.com/roaring/parallel.go:415:15: unnecessary conversion
os/src/github.com/roaring/roaring.go:71:16: unnecessary conversion
os/src/github.com/roaring/roaring.go:74:15: unnecessary conversion
os/src/github.com/roaring/roaring.go:614:16: unnecessary conversion
os/src/github.com/roaring/roaring.go:1881:27: unnecessary conversion
os/src/github.com/roaring/roaring.go:1885:26: unnecessary conversion
os/src/github.com/roaring/roaring.go:2041:27: unnecessary conversion
os/src/github.com/roaring/roaring.go:2045:26: unnecessary conversion
os/src/github.com/roaring/roaring.go:2143:32: unnecessary conversion
os/src/github.com/roaring/roaring.go:2144:25: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64.go:69:30: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64.go:751:40: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64.go:960:43: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64.go:1069:40: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:142:16: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:156:34: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:157:31: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:276:24: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:289:27: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:319:34: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:332:31: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:345:34: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:346:31: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:390:25: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:558:32: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:598:32: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:611:32: unnecessary conversion
os/src/github.com/roaring/roaring64/bsi64_test.go:788:16: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:76:13: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:122:16: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:170:16: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:172:13: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:252:47: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64.go:262:47: unnecessary conversion
os/src/github.com/roaring/roaring64/roaring64cow_test.go:273:30: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:14:24: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:14:39: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:15:24: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:15:39: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:16:24: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:16:40: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:52:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:52:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:53:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:53:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:54:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:54:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:55:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:55:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:57:43: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:58:43: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:62:42: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:63:42: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:97:26: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:104:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:104:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:105:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:105:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:106:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:106:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:107:27: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:107:41: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:109:43: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:110:43: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:114:42: unnecessary conversion
os/src/github.com/roaring/roaring64/roaringarray64_test.go:115:42: unnecessary conversion
os/src/github.com/roaring/roaring_test.go:375:23: unnecessary conversion
os/src/github.com/roaring/roaring_test.go:375:34: unnecessary conversion
os/src/github.com/roaring/roaring_test.go:376:23: unnecessary conversion
os/src/github.com/roaring/roaring_test.go:376:34: unnecessary conversion
os/src/github.com/roaring/roaringarray.go:593:16: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:377:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:378:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:488:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:489:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:608:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:609:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:710:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:711:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:838:10: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1036:10: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1130:12: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1131:7: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1160:75: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1184:14: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1257:25: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1298:25: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1407:23: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1533:10: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1560:20: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1561:17: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1569:20: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1570:17: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1575:25: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1576:32: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1581:32: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1638:17: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1655:20: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1656:17: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1667:20: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1668:17: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:1830:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:2469:10: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:2483:13: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:2489:12: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:2497:14: unnecessary conversion
os/src/github.com/roaring/runcontainer.go:2702:18: unnecessary conversion
os/src/github.com/roaring/runcontainer_test.go:518:38: unnecessary conversion
os/src/github.com/roaring/runcontainer_test.go:518:50: unnecessary conversion
os/src/github.com/roaring/runcontainer_test.go:2752:40: unnecessary conversion
os/src/github.com/roaring/serialization_frozen_test.go:129:10: unnecessary conversion
os/src/github.com/roaring/util.go:127:15: unnecessary conversion
os/src/github.com/roaring/util_test.go:12:24: unnecessary conversion
os/src/github.com/roaring/util_test.go:13:25: unnecessary conversion
os/src/github.com/roaring/util_test.go:20:24: unnecessary conversion
os/src/github.com/roaring/util_test.go:21:25: unnecessary conversion

Fullfills #118

[lemire]

Will be in the next release.

[DhruvilK7]

Will add a linter for the same in different PR