[Rust][Parquet] Implement returning dictionary arrays from parquet reader

[asfimport]

Currently the Rust parquet reader returns a regular array (e.g. string array) even when the column is dictionary encoded in the parquet file.

If the parquet reader had the ability to return dictionary arrays for dictionary encoded columns this would bring many benefits such as:

• faster reading of dictionary encoded columns from parquet (as no conversion/expansion into a regular array would be necessary)

• more efficient memory use as the dictionary array would use less memory when loaded in memory

• faster filtering operations as SIMD can be used to filter over the numeric keys of a dictionary string array instead of comparing string values in a string array

  [~nevime]  , @alamb  let me know what you think

Reporter: Yordan Pavlov / @yordan-pavlov

_{Note: This issue was originally created as ARROW-11410. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
@yordan-pavlov I think this would be amazing – and we would definitely use it in IOx. This is the kind of thing that is on our longer term roadmap and I would love to help (e.g. code review, or testing , or documentation, etc).

Let me know!

[asfimport]

Andrew Lamb / @alamb:
Migrated to github: apache/arrow-rs#171