[Format] Add Decimal32 and Decimal64 to Arrow

[zeroshade]

Describe the enhancement requested

Instead of adding entirely new types, we should widen the existing Decimal128/256 types to allow bit widths of 32 and 64.

This will require:

• Update specification and Schema.fbs documentation
• Implement basic type, arrays, builders, scalars
• Update compute / acero kernels with the new types
• Update Parquet implementation to leverage the new bitwidths where available
• Add test cases for Decimal32/Decimal64 to existing tests and integration test cases

Component(s)

Format