Is your feature request related to a problem or challenge? Please describe what you are trying to do.
In apache/arrow#49296 @pitrou found a clever optimization for delta packed decoding. If the bitwidth for a miniblock is 0, meaning a constant delta throughout the miniblock, then some optimizations can be made. Some pretty dramatic speedups were presented for the arrow-cpp decoder.

Describe the solution you'd like
Explore implementing a similar optimization in the parquet crate.

Describe alternatives you've considered
Leave it as is

Additional context