Spark: Support nested geospatial values in StructInternalRow

[charliec05]

Closes #17720

What changed

• Add robust conversion for nested GEOMETRY / GEOGRAPHY values in StructInternalRow, including list/map/struct collections for Spark 4.1.
• Handle WKB conversion via helper that supports both byte[] and ByteBuffer inputs and preserves correct SRID for GEOMETRY values.
• Add TestStructInternalRowGeospatial covering scalar and nested collection conversions, null handling, and byte[]/ByteBuffer inputs.

Testing

• ./gradlew --no-parallel --max-workers=2 -DsparkVersions=4.1 :iceberg-spark:iceberg-spark-4.1_2.13:test --tests org.apache.iceberg.spark.source.TestStructInternalRowGeospatial
• ./gradlew --no-parallel --max-workers=2 -DsparkVersions=4.1 :iceberg-spark:iceberg-spark-4.1_2.13:spotlessCheck

Notes

• This PR addresses issue Spark: Support nested geospatial values in StructInternalRow for older versions #17720 and adds support for nested geospatial values in StructInternalRow behavior for Spark 4.1.