REF: separate numpy-specific part of can_hold_element
By returning the value instead of just a bool, we open the option to return the _casted_ value, which is what we'll do in the follow-up, which will let us de-duplicate NumericIndex._validate_fill_value.  By separating out the np-specific parts, we'll be able to improve perf in a couple of places.
> would it be better to use None as the return value rathe than using exceptions as control flow ? (e.g. performance)

That becomes ambiguous with if the actual element is None.

There _are_ some performance concerns i have with this function, but try/except overhead is not among them. > There are some performance concerns i have with this function, but try/except overhead is not among them.

oh ok.