arrow

GH-41692: [Python] Improve substrait extended expressions support (#41693)

Addresses some missing features and usability issues when using PyArrow
with Substrait ExtendedExpressions
* GitHub Issue: #41692

- [x] Allow passing `BoundExpressions` for `Scanner(columns=X)` instead
of a dict of expressions.
- [x] Allow passing `BoundExpressions` for `Scanner(filter=X)` so that
user doesn't have to distinguish between `Expression` and
`BoundExpressions` and can always just use
`pyarrow.substrait.deserialize_expressions`
- [x] Allow decoding `pyarrow.BoundExpressions` directly from
`protobuf.Message`, thus allowing to use substrait-python objects.
- [x] Return `memoryview` from methods encoding substrait, so that those
can be directly passed to substrait-python (or more in general other
python libraries) without a copy being involved.
- [x] Allow decoding messages from `memoryview` so that the output of
encoding functions can be sent back to dencoding functions.
- [x] Allow to encode and decode schemas from substrait 
- [x] When encoding schemas return the extension types required for a
substrait consumer to decode the schema
- [x] Handle arrow extension types when decoding a schema
- [x] Update docstrings and documentation

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Co-authored-by: Raúl Cumplido <raulcumplido@gmail.com>