feat: Partition memtables by time if compaction window is provided

[evenyag]

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What's changed and what's your intention?

This PR introduces a new struct TimePartitions to partition mutable memtables by time.

• It uses the compaction time window (compaction.twcs.time_window) as the partition time range
• Each partition holds timestamps between [start_time, start_time + time_window)
• We uses the timestamp / time_window * time_window to locate the proper partition
• If the compaction time window is not provided, it only has one partition and all timestamps belong to that partition
• Once we freeze a memtable version, we move all memtables in TimePartitions to immutable memtable list.

With this feature, a region can strictly divide data by the time in memory. It also ensures flushed SSTs only belong to a single time window.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[codecov]

Codecov Report

Attention: Patch coverage is 90.60773% with 51 lines in your changes are missing coverage. Please review.

Project coverage is 84.95%. Comparing base (58bd065) to head (759e84a).
Report is 6 commits behind head on main.

❗ Current head 759e84a differs from pull request most recent head eda062f. Consider uploading reports for the commit eda062f to get more accurate results

Additional details and impacted files

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- Coverage   85.35%   84.95%   -0.41%     
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  Files         903      905       +2     
  Lines      149639   150400     +761     
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+ Hits       127726   127770      +44     
- Misses      21913    22630     +717     

[fengjiachun]

LGTM

[v0y4g3r]

LGTM