CI: add minimal requirements file
- [ ] closes #48828 (Replace xxxx with the GitHub issue number)
- [ ] [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
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Love the idea - needed something similar for #50046 

Wondering if we shouldn't make this actually a minimal requirements file though, which would exclude pytest-cov and pytest-xdist (I think only CI needs those). Might be nice to have a true minimal file and compose the CI required-elements on top of that Any other thoughts on this? @mroeschke @lithomas1 @fangchenli  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. We've got 2 approvals on this. Rather then let it go stale let's merge in on next conflict fixup, unless someone objects this workflow isn't actually running at the moment, so marking as draft until it's re-enabled https://github.com/pandas-dev/pandas/pull/50696#discussion_r1100477141 closing to clear the queue, might pick it up again in the future