BUG: BooleanArray.value_counts dropna
Closes https://github.com/pandas-dev/pandas/issues/30685
LGTM pending green OK, updated {String,Integer,Boolean}Array.value_counts to return a nullable int64 dtype.

I moved BooleanArray.value_counts and IntegerArray.value_counts to the base class. let me clarify my comments

i think the index should be nullable ints as that preserves the intent here
but agree the values should be int64 - this is a count after all Thanks for clarifying.

The index can't be nullable yet. @jorisvandenbossche thoughts on the values dtype? > Ideally we'd retain the dtype in the value_counts().index, and it seems like we're saying here "well we cant do that, so let's shoehorn the dtype into the values"

IMO, ideally we retain the nullable dtype in *both* the index and the values. But indeed, for index we can't do that yet, so for now it's only the values.

>  It seems weird that the values would be anything other than np.int64

We are still returning an int dtype. But in the "nullable dtype universe"-subsystem, the "int64" dtype is the nullable int64 dtype.


 So I think that's some +1s and a -0 (https://github.com/pandas-dev/pandas/pull/30824#discussion_r364862869). Merging in an hour or so unless @jbrockmendel objects. No objection here. Thanks.