[improvement](show backends) show backends print trash used

[yujun777]

Proposed changes

When executing sql command show backends, if there's a lot of trash, users will found DataUsedCapacity + AvailCapacity is far less than TotalCapacity. They may be confused. So print used trash capacity to make them better understand.

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

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[hello-stephen]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 48.08 seconds
stream load tsv: 529 seconds loaded 74807831229 Bytes, about 134 MB/s
stream load json: 20 seconds loaded 2358488459 Bytes, about 112 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: 29.0 seconds inserted 10000000 Rows, about 344K ops/s
storage size: 17162087454 Bytes

[yujun777]

run buildall

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[hello-stephen]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 46.8 seconds
stream load tsv: 531 seconds loaded 74807831229 Bytes, about 134 MB/s
stream load json: 20 seconds loaded 2358488459 Bytes, about 112 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: 29.0 seconds inserted 10000000 Rows, about 344K ops/s
storage size: 17161857946 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.

[sollhui]

LGTM

[wm1581066]

LGTM