fix(python, rust): enforce sortedness of by argument in rolling_* functions

[MarcoGorelli]

closes #10991

[orlp]

I believe we shouldn't merge this, please see my concerns here: #10991.

[MarcoGorelli]

Sure, closing then

---

Actually, reopening

I agree with the concerns raised in #10991, and agree that the proposed solution (temporary sort) is better than this PR

But, if nobody has time* to implement the proposed solution from #10991 in time for 0.19.3 (which I presume will come out some time next week?), then I'd still like to suggest that this PR is better than the status-quo (which silently gives wrong results)

After all, upsample, group_by_rolling, and group_by_dynamic all already do what this PR proposes

*I'm travelling at the moment so don't really have time for anything non-trivial unfortunately

Polars downloads are exploding and I'm worried that someone might get wrong results and lose faith in the library

[orlp]

I would not mind merging it as long as it's a temporary stopgap until we fix the feature to always work.

[ritchie46]

Let's temporary require this flag. @MarcoGorelli can you rebase?

[MarcoGorelli]

First time I try rebasing from my phone whilst on a ferry and it seems to not have worked 😄 Will address this evening, and will make sure to remove the temporary stopgap early next month