EA concat_same_type vs Index concat_same_dtype?
Working on making making the DatetimeLike ArrayMixin classes into full-fledged EA subclasses, I need to implement `_concat_same_type`.  The Index subclasses already have `_concat_same_dtype`, which looks like it implements the right thing.

Should we rename the Index method to match the EA name?  Or do these need to stay separate?