GH-3679: Allow TimestampType to annotate FLBA(12)

[divjotarora]

Rationale for this change

See parquet-format issue apache/parquet-format#600 and the linked proposal document for rationale

What changes are included in this PR?

This PR implements support for the TimestampType logical type annotation on FIXED_LEN_BYTE_ARRAY physical type values with type_length=12 (96 bits).

Are these changes tested?

Yes, several test files are updated along with the source.

Are there any user-facing changes?

Users will be able to declare schemas with this physical/logical type combination. No API changes.

Closes #3679

[stevomitric]

Should the converted_type be suppressed for the FLBA(12) carrier, the same way NANOS already returns empty? Those legacy types are defined as INT64-only, so emitting them here gives a contradictory footer.

[divjotarora]

Should the converted_type be suppressed for the FLBA(12) carrier, the same way NANOS already returns empty? Those legacy types are defined as INT64-only, so emitting them here gives a contradictory footer.

Thanks for catching @stevomitric, the existing tests didn't catch this because they were focusing on using FLBA(12) with NANOS and it doesn't have a converted type already. The code is now fixed and there are more tests to validate FLBA(12) with MILLIS and MICROS as well.