Fix regression ignoring arrays in dtype check for merge_asof
- [x] closes #42844
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [x] whatsnew entry

This restores the 1.2.x behavior.

Passing an array as join key is something we don't have much test support. We have 2 tests for this which were added ages ago. We could deprecate this.