[fix](tablet clone) fix be load rebalancer choose candidate tablets

[yujun777]

Proposed changes

When be load reblancer choose candidate tablets, it will try moving tablets from high load backends to low backend backends. If the higher HIGH BE has no available slot num, it should try next HIGH BE.

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[yujun777]

run buildall

[doris-robot]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 45.91 seconds
stream load tsv: 527 seconds loaded 74807831229 Bytes, about 135 MB/s
stream load json: 21 seconds loaded 2358488459 Bytes, about 107 MB/s
stream load orc: 64 seconds loaded 1101869774 Bytes, about 16 MB/s
stream load parquet: 32 seconds loaded 861443392 Bytes, about 25 MB/s
insert into select: 28.9 seconds inserted 10000000 Rows, about 346K ops/s
storage size: 17162151846 Bytes

[dataroaring]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.

[shuke987]

run buildall

[doris-robot]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 45.98 seconds
stream load tsv: 530 seconds loaded 74807831229 Bytes, about 134 MB/s
stream load json: 21 seconds loaded 2358488459 Bytes, about 107 MB/s
stream load orc: 64 seconds loaded 1101869774 Bytes, about 16 MB/s
stream load parquet: 31 seconds loaded 861443392 Bytes, about 26 MB/s
insert into select: 28.7 seconds inserted 10000000 Rows, about 348K ops/s
storage size: 17161960809 Bytes

[yiguolei]

LGTM