feat!: Removes `inplace` option for `pandas.core.resample.Resampler.i…
…nterpolate`. Fixes / cleans up related test cases.

- [x] closes #58690 (Replace xxxx with the GitHub issue number)
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

@MarcoGorelli somehow it did not auto-assign the reviewers. But in any case, here we are :) Do these need to be deprecated first? You can use the `deprecate_kwarg` decorator for that > Do these need to be deprecated first? You can use the `deprecate_kwarg` decorator for that

I don't know what the exact policy is. But as far as I understand the deprecation tells the user that a certain **future** change will change the API. This does not apply here, as the inplace-functionality is already broken. We would need to add the deprecation to pandas 2 to inform users about the upcoming change, and to ease migration. But I guess this would need a separate PR that targets the next 2.x release. > Do these need to be deprecated first?

Thanks @Aloqeely - in general, yes, this would require a deprecation. However, here, the change is going to breaking anyway (in order to fix a historic ~~feature~~ bug), so to be honest I'd be OK removing `inplace` without warning too @mroeschke can we merge this? 😄  This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. > This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this.

I'll work on this, I was just unable to spend time. Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.