Add ConfigOptions convenience class to cudf-polars

[rjzamora]

Description

I propose that we add a simple management utility for GPUEngine configuration options in cudf-polars.

In order to support a variety of configurable groupby/shuffle/sort/join options for multi-gpu execution, we will want to make it easy to pass through these options to IR nodes at translation time. We will also want it to be "easy" set/get specific options at traversal/evaluation time.

Checklist

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

[vyasr]

We may want to introduce a dedicated ExecutorOptions class to manage these kinds of configuration options, but I don't personally have the bandwidth to iterate on a solid API. Therefore, I'm proposing that we keep it as a simple dictionary for now, and use a convenience API to manage that dictionary until we have a better design in mind.

OK that's fine with me then.

[rjzamora]

@wence- I'd like to get this in after #17503, unless you think 17503 needs more work (in which case, I'd like to merge this so I can clean up config handling across several multi-gpu PRs)

[wence-]

Thanks Rick

[rjzamora]

/merge