feat: Enable Arrow to convert nullable StructArray to RecordBatch

[DrakeLin]

🥞 Stacked PR

Use this link to review incremental changes.

• stack/propagate-nulls [Files changed]
  • stack/nullable-transform [Files changed]
    • stack/has_compatible_parsed_stats [Files changed]
      • stack/read-parsed-stats [Files changed]

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What changes are proposed in this pull request?

Change apply_schema to propagate top-level struct nulls to child columns instead of erroring

• Remove the error check for top-level nulls in apply_schema
• Document that child columns are expected to already have nulls propagated (Arrow's JSON reader does this automatically, and parquet data goes through fix_nested_null_masks)
• Add comprehensive test case test_apply_schema_handles_top_level_null

How was this change tested?

Edited unit tests

Added unit test to show new behavior

[codecov]

Codecov Report

❌ Patch coverage is 81.39535% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.16%. Comparing base (07083a1) to head (e5beaf9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
kernel/src/engine/arrow_expression/apply_schema.rs	81.39%	0 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1635      +/-   ##
==========================================
- Coverage   84.16%   84.16%   -0.01%     
==========================================
  Files         123      123              
  Lines       34179    34214      +35     
  Branches    34179    34214      +35     
==========================================
+ Hits        28767    28796      +29     
  Misses       4021     4021              
- Partials     1391     1397       +6     

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[dengsh12]

LGTM, amazing to learn the Arrow's JSON reader does this automatically

[nicklan]

lgtm, thanks for looking into this!