Consider adding ExtensionDtype.is_dtype_equal

[TomAugspurger]

We have is_dtype for checking whether the dtype / array's dtype is of the same kind as self. It may sometimes be useful to have an exact comparison for parametrized dtypes like Categorical and Period.

So

>>> PeriodDtype('4D').is_dtype(PeriodDtype('5D'))
True
>>> PeriodDtype('4D').is_dtype_equal(PeriodDtype('5D'))

[jbrockmendel]

I guess this would be faster than __eq__ bc it would assume we have a Dtype object and not a string

[phofl]

Yeah this works with Eq, so closing