GH-3832: Preserve component paths in column configuration

[costas-db]

What changes?

Add a backward-compatible structured form for per-column Hadoop configuration keys. Each UTF-8 path component is encoded independently, so the valid paths ["a.b"] and ["a", "b"] no longer collapse to the same "a.b" identity.

The PR adds:

• component-aware parsing and key generation in ColumnConfigParser
• String[] path overloads for Bloom-filter and statistics properties
• public ParquetOutputFormat setters for those structured paths
• round-trip coverage for dotted, nested, empty, and Unicode path components
• an end-to-end statistics regression using ordinary string columns

Legacy dot-string keys continue to work. Structured overrides are applied afterward, so callers can opt into unambiguous paths without a compatibility break. This does not change the Parquet file format.

Why is this needed?

Per-column configuration currently passes a flattened string into ColumnPath.fromDotString. A top-level field literally named a.b is therefore indistinguishable from nested field b under a; configuration intended for one column can be applied to the other. The issue is datatype-independent.

TDD verification

The first commit adds the reproduction before production changes. On master, it fails because the top-level ["a.b"] override is ignored. The second commit adds the structured-path implementation.

Final verification:

• TestParquetProperties: 11 tests passed
• TestParquetWriter: 32 tests passed
• TestColumnConfigParser: 1 test passed
• Spotless passed
• Apache RAT passed

Fixes #3832