feat: Implements row group level parallel unordered scanner

[evenyag]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

• Support parallel scan in mito engine #2806

What's changed and what's your intention?

This PR changes the UnorderedScan to read parquet row groups in parallel to improve scan performance. It also implements the RegionScanner trait for UnorderedScan.

• Adds build_parts method to ScanInput to collect all FileRanges (row groups) and memtables
  • ranges and memtables are distributed by parallelism
• UnorderedScan can return parallelism streams
• Adds CompatBatch to adapt batch schema.
  • We might remove the CompatReader in the future as CompatBatch doesn't require implementing the BatchReader trait.

It also defines a ScanPartBuilder trait to allow different parallel scan strategies.

pub(crate) trait ScanPartBuilder {
    fn set_parallelism(&mut self, parallelism: usize);

    fn append_file_ranges(&mut self, file_ranges: impl Iterator<Item = FileRange>);

    fn build_parts(self, memtables: &[MemtableRef]) -> Vec<ScanPart>;
}

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

[codecov]

Codecov Report

Attention: Patch coverage is 80.85938% with 49 lines in your changes are missing coverage. Please review.

Project coverage is 85.01%. Comparing base (dfc1acb) to head (c10f839).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3992      +/-   ##
==========================================
- Coverage   85.44%   85.01%   -0.43%     
==========================================
  Files         980      987       +7     
  Lines      170140   171396    +1256     
==========================================
+ Hits       145379   145716     +337     
- Misses      24761    25680     +919     

[fengjiachun]

LGTM

[waynexia]

🛫