GH-41692: [Python] Improve substrait extended expressions support

[amol-]

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

• [ ] Handle arrow extension types when decoding a schema

• [ ] Update docstrings and documentation

[github-actions[bot]]

:warning: GitHub issue #41692 has been automatically assigned in GitHub to PR creator.