Parquet: Handle decimal and UUID literals in filter pushdown

[laserninja]

Summary

Handle BigDecimal and UUID literal types in ParquetFilters to enable filter pushdown for decimal and UUID predicates.

Problem

Closes #16035

ParquetFilters.getParquetPrimitive() throws UnsupportedOperationException for BigDecimal and UUID values. Additionally, decimal predicates were always routed through binaryColumn() regardless of precision, producing incorrect Parquet filter predicates for decimals that are stored as INT32 or INT64.

Solution

• Decimal: Route predicates through the correct Parquet column type based on precision:
  • intColumn for precision ≤ 9 (stored as INT32)
  • longColumn for precision ≤ 18 (stored as INT64)
  • binaryColumn for precision > 18 (stored as FIXED_LEN_BYTE_ARRAY)
  • Added helper methods getDecimalAsInt(), getDecimalAsLong(), and getDecimalAsBinary() for the conversions
• UUID: Convert via UUIDUtil.convert() to 16-byte Binary in getParquetPrimitive()

Testing

• Existing tests pass (./gradlew :iceberg-parquet:test)
• Added TestParquetFilters with 10 tests covering:
  • All three decimal precision tiers (INT32, INT64, FIXED_LEN_BYTE_ARRAY)
  • Decimal comparison predicates (lt, lte, gt, gte)
  • Decimal null/notNull predicates on optional fields
  • UUID equality and comparison predicates
  • UUID null/notNull predicates on optional fields
  • Regression tests for string and integer filter pushdown
• ./gradlew spotlessApply passes

Note: This contribution was AI-assisted. The implementation logic and design decisions were reviewed and verified by the author.