fix: make Parquet file schema type coercion work on nested schemas

[adragomir]

• ATM, the Parquet file schema type coercion applies view transforms for example only on top-level fields, but not on nested fields.
• For some Parquet schemas, where we request a view transform for a nested field, this is translated to an unmodified schema passed to the reader. Then, when we try to apply predicates on the actual data on that nested field, the actual predicate execution needs a cast, because the schemas are different - the predicate refers to a string view, but the actual data schema refers to a string

Which issue does this PR close?

• Closes Parquet schema file type coercion functionality is not applied on all fields in nested schemas, only on the top-level fields #25192

Rationale for this change

• Rationale is explained in Parquet schema file type coercion functionality is not applied on all fields in nested schemas, only on the top-level fields #25192
• Also, I don't see any reason (explicit comments) why this function would not work on deeply nested schemas

What changes are included in this PR?

• Modification of the apply_file_schema_type_coercions function to work on nested fields
• Respective tests for the functionality

What is the testing strategy for this PR?

• All tests pass
• Newly added unit tests pass

Are there any user-facing changes?

• Unsure ? Probably not ? The documentation in the function does NOT explicitly say the current behavior.

[aditanase]

cc @adriangb - this is closely related with the nested schema pruning work that is ongoing. We discovered this by investigating a 2x slowdown on delta-rs next vs old TableProviders. Turned out that inconistent Utf8View handling in nested schemas was triggering the more expensive Utf8 decoding unnecessary

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.52381% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.92%. Comparing base (517ac6d) to head (3248cda).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...tafusion/datasource-parquet/src/schema_coercion.rs	99.52%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #25193    +/-   ##
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  Coverage   81.91%   81.92%            
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  Files        1132     1132            
  Lines      421311   421520   +209     
  Branches   421311   421520   +209     
========================================
+ Hits       345137   345337   +200     
- Misses      55768    55774     +6     
- Partials    20406    20409     +3     

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