add --processing:dots|filenames|off to customize hintProcessing

[timotheecour]

• add --processing:dots|filenames|off to customize hintProcessing, which allows bringing back the old hintProcessing (but better, because it honors --filenames:...)
• fixes hintProcessingVerbose timotheecour/Nim#502
• remove duplication bw newPartialConfigRef and newConfigRef
• minor cleanups post --filenames:abs|canonical|legacyRelProj for filenames in compiler msgs (replaces --listfullpaths:on|off) #17746 (removing remaining uses of --listfullpaths)

example 1

nim r --processing:filenames --filenames:canonical --hint:msgorigin:off --eval:'import times'
Hint: system.nim [Processing]
Hint: system/widestrs.nim [Processing]
Hint: system/io.nim [Processing]
Hint: cmdfile.nim [Processing]
Hint: std/times [Processing]
Hint: std/strutils [Processing]
Hint: std/parseutils [Processing]
Hint: std/math [Processing]
Hint: std/bitops [Processing]
Hint: std/macros [Processing]
Hint: std/fenv [Processing]
Hint: std/algorithm [Processing]
Hint: std/enumutils.nim [Processing]
Hint: std/typetraits [Processing]
Hint: std/unicode [Processing]
Hint: std/private/strimpl.nim [Processing]
Hint: std/options [Processing]
Hint: std/posix [Processing]
cmdfile.nim(1, 8) Warning: imported and not used: 'times' [UnusedImport]

example 2

nim r --processing:dots --filenames:canonical --hint:msgorigin:off --eval:'import times'
..................
cmdfile.nim(1, 8) Warning: imported and not used: 'times' [UnusedImport]

example 3

nim r --processing:filenames --filenames:abs --hint:msgorigin:off --eval:'import times'
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/system.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/system/widestrs.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/system/io.nim [Processing]
Hint: cmdfile.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/times.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/strutils.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/parseutils.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/math.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/bitops.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/core/macros.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/fenv.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/algorithm.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/std/enumutils.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/typetraits.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/unicode.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/std/private/strimpl.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/pure/options.nim [Processing]
Hint: /Users/timothee/git_clone/nim/Nim_prs/lib/posix/posix.nim [Processing]
cmdfile.nim(1, 8) Warning: imported and not used: 'times' [UnusedImport]

future work

• also report include files, either as default or as an option eg --processing:filenames,includes

[timotheecour]

if child already died, these could raise an IOError os OSError with EPIPE (or, before #17752, raise signal SIGPIPE), so it seems correct to protect this with try/except;

this diff is not needed for this PR but it helped during debugging and fixing tests as raise EPIPE would hide the error