BUG/WARN: Passing EA object to dtype instead of an instance
- [x] closes #31356 (Replace xxxx with the GitHub issue number)
- [x] closes #54592 (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).
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Instantiating an empty instance is an imperfect solution since the EADtype could require positional arguments, so raises a UserWarning to encourage users to pass instances instead 

> LGTM. Is the end-goal to deprecate this in the future?

I don't think there has been formal discussion to deprecate, but I would +1 for deprecating in the future. 