Preserve partitioning metadata after simple Select operations

[rjzamora]

Description

Some projection operations show up in the Polars plan as Select with simple Col expressions. We can preserve partitioning metadata when this is the case.

Part of #20482

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[TomAugspurger]

Tests all look good. I think you covered all the cases I was wondering about (e.g. reordering). Just a couple questions on the implementation.

[rjzamora]

/merge