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ARROW-8426: [Rust] [Parquet] - Add more support for converting Dicts

This adds more support for:

- When converting Arrow -> Parquet containing an Arrow Dictionary,
materialize the Dictionary values and send to Parquet to be encoded with
a dictionary or not according to the Parquet settings (deliberately not supporting
converting an Arrow Dictionary directly to Parquet DictEncoding, and right now this only supports String dictionaries)
- When converting Parquet -> Arrow, noticing that the Arrow schema
metadata in a Parquet file has a Dictionary type and converting the data
to an Arrow dictionary (right now this only supports String dictionaries)

I'm not sure if this is in a good enough state to merge or not yet, please let me know @nevi-me !

Closes #8402 from carols10cents/dict

Lead-authored-by: Carol (Nichols || Goulding) <carol.nichols@gmail.com>
Co-authored-by: Neville Dipale <nevilledips@gmail.com>
Co-authored-by: Jake Goulding <jake.goulding@gmail.com>
Signed-off-by: Neville Dipale <nevilledips@gmail.com>