feat: add geospatial read support [2/3]

[wirybeaver]

Summary

Part 2 of the geospatial support stack. Depends on #2933.

• Converts Iceberg geometry/geography fields to Arrow WKB extension fields and imports valid WKB extension metadata back into Iceberg types.
• Validates binary Arrow storage and rejects malformed CRS metadata.
• Preserves supplied CRS identifiers without semantic canonicalization.
• Reads WKB values through Arrow and Avro byte representations.
• Ignores scalar Parquet min/max statistics for geospatial fields so row-group pruning cannot compare WKB bytes as ordered scalar bounds.

For the review-only delta over part 1: wirybeaver/iceberg-rust@support-geometry-geography-types...support-geometry-geography-read

Tests

• cargo check -p iceberg --locked
• cargo test -p iceberg geospatial
• cargo test -p iceberg avro_bytes_geometry