feat: Defines more structs and methods for a partitioned merge tree

[evenyag]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

This PR defines more methods and structs related to Partition and Shard for the merge tree.

• The Partition provides two methods write_with_key() and write_no_key() to write a row with or without a primary key
• We can scan the partition by the scan() method
• We can also freeze or fork a partition
• Shard also has similar methods
• We use the value of __table_id column as partition key
• The merge tree finds a partition according to the partition key to a row
• The merge tree will try to prune partitions by filters to reduce the number of partitions to scan
• Implements freeze(), fork() for the merge tree

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.

Refer to a related PR or issue link (optional)

• Tracking issue for the memtable improvement #2804

[codecov]

Codecov Report

Attention: 260 lines in your changes are missing coverage. Please review.

Comparison is base (f087a84) 85.24% compared to head (51c57d2) 84.72%.
Report is 9 commits behind head on main.

Additional details and impacted files

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##             main    #3348      +/-   ##
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- Coverage   85.24%   84.72%   -0.52%     
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  Files         882      887       +5     
  Lines      144085   144657     +572     
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- Hits       122823   122563     -260     
- Misses      21262    22094     +832     

[fengjiachun]

LGTM

[v0y4g3r]

LGTM