Add support for Equality Deletes on DeleteFileIndex

[rambleraptor]

Part of #3270

Rationale for this change

This adds support for getting equality deletes in the DeleteFileIndex.

I'm very purposefully ignoring them in _read_all_delete_files because they will crash.

Are these changes tested?

I made some equality deletes by-hand and had PyIceberg read them to see the indexes. Worked as expected. If you know a way to create equality deletes, I can test those as well.

Are there any user-facing changes?

• Adds support for equality deletes in DeleteFileIndex

[ndrluis]

@rambleraptor I think we should add a regression test for schema evolution here. This pruning path assumes the current table type for an equality field is the same type that was used when the data file and equality delete were written, which is not always true after a legal promotion like int -> long. In that case, historical manifests still contain 4-byte int bounds, and decoding them with the current LongType can fail in DeleteFileIndex.for_data_file(...).

For reference, Iceberg Java had to address the same schema-evolution issue in apache/iceberg#15268, where the fix was to avoid assuming the current schema is always the right one for equality-delete field resolution.