perf: Partition metadata for parquet statistic loading

[ritchie46]

fixes #18319

I am convinced we need a metadata supertype so we can amortize this as we need this all over.
We also need the arrow schema to be backed by an IndexSet. Currently we need a linear search to get a dtype.

[codecov]

Codecov Report

Attention: Patch coverage is 78.65169% with 19 lines in your changes missing coverage. Please review.

Project coverage is 79.82%. Comparing base (5cfc1f0) to head (dd1615d).
Report is 1 commits behind head on main.

Files	Patch %	Lines
crates/polars-stream/src/nodes/parquet_source.rs	0.00%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18343      +/-   ##
==========================================
- Coverage   79.84%   79.82%   -0.03%     
==========================================
  Files        1496     1496              
  Lines      200313   200333      +20     
  Branches     2841     2841              
==========================================
- Hits       159942   159916      -26     
- Misses      39846    39892      +46     
  Partials      525      525              

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