Interval dtype fix
- [x] closes #25283
- [x] test added to ensure pd.api.types.IntervalDtype('IntervalA') throws TypeError
- [x] test added to ensure pd.api.types.IntervalDtype.construct_from_string('IntervalA') throws TypeError
- [x] test added to ensure pd.api.types.IntervalDtype.is_dtype('IntervalA') returns false
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] test added to ensure * `Series(['IntervalA', 'IntervalB', 'IntervalC']) == 'IntervalA'` returns the expected boolean series
- [x] what's new note added to doc/source/whatsnew/v0.24.2.rst documenting regression fix