feat: override __sequence on creating SST to save space and CPU

[waynexia]

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Refer to a related PR or issue link (optional)

What's changed and what's your intention?

The sequence is u64 and is allocated with write request. They are different from row to row and thus has bad compression efficiency in both CPU and space. We can assign the greatest sequence number to the file to reduce this overhead while keeping this mechanism works.

In TSBS test scenario with 100M rows, it can save 48MB of disk space. And in the metric monitor scenario, it can save up to 50%~60% in file size. We can also observe an (unstable) flush performance improvement.

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

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[codecov]

Codecov Report

Attention: Patch coverage is 98.34711% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.69%. Comparing base (588f675) to head (e188d7d).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5252      +/-   ##
==========================================
- Coverage   83.93%   83.69%   -0.24%     
==========================================
  Files        1203     1204       +1     
  Lines      224150   224613     +463     
==========================================
- Hits       188143   187998     -145     
- Misses      36007    36615     +608     

[MichaelScofield]

good for merging ssts when ingesting them, better if the __sequence can be removed

[evenyag]

good for merging ssts when ingesting them, better if the __sequence can be removed

We can share the same sequence because here we assume we always dedup all rows in the SST in non append-only mode.

[fengjiachun]

LGTM