[ENH]row_to_names for polars

[samukweku]

PR Description

Please describe the changes proposed in the pull request:

• Add row_to_names method for polars

**This PR relates to #1352 **

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Relevant Reviewers

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• @ericmjl

[ericmjl]

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[ericmjl]

@samukweku it looks like this one also needs to have merge conflicts resolved before we can continue. Would you be kind enough to take a look at it please?

[ericmjl]

@samukweku it looks like merging other polars dataframe functions results in large merge conflicts, which may make further development on the polars implementation of functions a bit more tricky. We may need to think carefully about how the code is organized here.

Do you think there is a way to leverage the polars API to create a polars-flavor package, not unlike the pandas-flavor package that we currently maintain? I think that would be the easiest way for us to handle the matter.

I tried thinking of a few other strategies, but none of them seem satisfactory. This included dynamically monkey-patching the docstrings of the PolarsFrame class methods from the underlying implementation function. But that has problems, just like other ideas I thought of, and didn't seem satisfactory.

[samukweku]

@ericmjl i thought of going with the pandas_flavor format but decided against it (polars has three namespaces which we support - lazyframe, expr and eager frames - it would be an issue in the docs rendering for these namespaces) - so i chose another route, creating 3 files for each of the namespaces. Still not sure if this is good enough - hopefully there is a better way. or maybe there is a better way to modify pandas_flavor to better support the namespaces?

[ericmjl]

@samukweku that's a good point, I didn't think of that.