Specialize FixedLenByteArrayReader for Parquet

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

We have optimised implementations for reading most types directly to their arrow representations, however, we fallback to reading FixedLenByteArray and then using ComplexObjectArrayReader to cast it to the desired type.

This is problematic for a couple of reasons:

• We want to remove ComplexObjectArrayReader - Remove ComplexObjectArrayReader #1661
• FixedLenByteArray has a Box<[u8]> which is very expensive

Describe the solution you'd like

I would like an optimized FixedLenByteArrayReader<const N: usize> that can be used to efficiently read values where the type is known up front, e.g. decimals and intervals. We can fallback to using FixedLenByteArray for the general case.

Describe alternatives you've considered

We could not do this

Additional context

[liukun4515]

If your pr ready, feel free to at me and request me to review
@tustvold