[PyRSA]

Purpose

Extend Rust Native merge_map_with_keytime to support additional key-time types and align its comparison and merge semantics with existing implementations.

Brief change log

• Support CHAR/VARCHAR, integer, FLOAT/DOUBLE, DATE, TIME, DECIMAL, TIMESTAMP, and TIMESTAMP_LTZ key-time types.
• Use UTF-16 code unit ordering for string comparisons to match Java String.compareTo.
• Align floating-point comparisons with Python semantics, including NaN and signed zero handling.
• Compare timestamp values using their underlying ticks.
• Support overwrite-on-equal-ts to control whether equal key-times replace existing values.
• Share key-time configuration resolution and type validation between table validation and aggregator construction.
• Reject unsupported key-time types during table creation.
• Preserve existing NULL key-time, NULL ROW tombstone, and regular merge_map behavior.

Tests

• spec::aggregation::tests: 23 passed.
• merge_map::tests: 16 passed.
• cargo fmt --check passed.
• git diff --check passed.

API and Format

No public API or file format changes.

Documentation

Update SQL documentation with supported key-time types, comparison semantics, and overwrite-on-equal-ts behavior.