REF: use common utilities when implementing EA._get_common_dtype

[mzeitlin11]

From #43409, #43409 (comment).

Look to use is_*_dtype instead of isinstance when implementing _get_common_dtype for EA's.

[jbrockmendel]

is_*_dtype in general is very slow

[jreback]

i think we should fix that (eg there was a fast path pr from joris or tom) i think at some point

[mroeschke]

I think we've settle on kind and isinstance checks as the common pattern now so closing