feat: add all methods of RPolarsExpr to RPolarsSeries

[eitsupi]

Instead of the experimental <Series>$expr$<method>, we can call methods that exist only in Expr with <Series>$<method>.

[eitsupi]

@etiennebacher I would like to merge this for a new release. Could you help me merge it?

[etiennebacher]

I can review in a couple of hours

[etiennebacher]

That looks good to me, thanks!

Now that the method dispatch is made automatically, can you remove the old implementation of the methods for Series? For example it's no longer necessary to implement Series_add ourselves. Note however that some methods cannot be removed because they should return a scalar and not a Series (e.g $sum(), $mean()...)

[eitsupi]

Now that the method dispatch is made automatically, can you remove the old implementation of the methods for Series?

Of course it is possible, but most of the existing methods look like thin wrappers for Rust Polars, so I think it might as well be left as they are.

In other words, what is here needs to be implemented on the Rust side as before, but the rest needs to be brought in from Expr.
https://docs.rs/polars/0.37.0/polars/series/struct.Series.html

[etiennebacher]

I get that some methods must be implemented in Rust because either they don't have equivalent in Expr or the Expr method would return a Series instead of a scalar. But other Series methods could simply be removed from the Rust and R sides and nothing would change, e.g $floor(), $ceiling().

I don't want this to be a blocker for this PR, but I think we should get rid of them to reduce the codebase.

[etiennebacher]

Apart from that, thank you for this PR, it's super useful to dispatch methods like this

[eitsupi]

Thanks for reviewing this. I will merge it and release it.

[eitsupi]

Sorry, the commit comment for the merge commit was broken due to browser behavior.