[DISC] Import the rlang package

[eitsupi]

Related to #939 (and potentially #367)

With limited development resources, I don't want to reinvent the wheel any further with what rlang has to offer.
I think there used to be value in not having dependencies to install binary packages on GitHub releases, but I don't see much value in not having dependencies now that installing from the R-universe works so well.

rlang is very widely used and rlang itself is a very small dependency since it does not depend on any other package.

Pros

• Features such as trailing commas and dot checks will be available.

Cons

• This will be the first external required dependency.

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@etiennebacher @sorhawell @vincentarelbundock @grantmcdermott @Sicheng-Pan Thoughts?

[etiennebacher]

I think it is overkill to import rlang just for a couple of functions, I never feel I'm missing this kind of functionalities when developing polars. My point of view might change if we were missing many utils but for now I simply don't see the need

[eitsupi]

Recently to enforce named arguments with ... is increasingly used, and given the frequency with which Polars change argument names, it would be worthwhile to use the rlang::check_dots_empty() function to check arguments to reduce implicit failures for the user.

I am not sure how much emphasis on no dependencies is worth.

[eitsupi]

Closing in favor of #1152