DEPR: __invert__ on non-bool dtypes

ATM we allow `~obj` with any dtype, but the pyarrow dtypes only allow it with boolean dtype. We should be consistent here, either allowing it for all dtypes or for only-bool dtypes. On a call with @mroeschke and @jorisvandenbossche a couple weeks ago we were leaning towards only-bool, though I forget the exact reasoning. Either of you remember?