Support Format Spec 1.5 - Decimal32/64

### Describe the enhancement requested

Arrow Format 1.5 was released on Sep 10, 2024 and Arrow java should support that version instead of being stuck on 1.4. This means we need to add support for Decimal32/64

Start by locating Arrow Java's current Arrow Format 1.4 support and the existing decimal type definitions. Compare those paths with the Arrow Format 1.5 specification, then verify that Decimal32 and Decimal64 are represented and handled consistently wherever format support is tested. Done means Arrow Java supports the requested 1.5 decimal types without remaining 1.4-only behavior.

Written by the indexing model from the issue text.