Permit selection with a list/array of keys

[flexatone]

StaticFrame, loc_to_iloc does this when given an iterable of labels (either a list or an array), where label_to_pos is an AM or FAM.

            if partial_selection:
                return [label_to_pos[k] for k in key if k in label_to_pos] # type: ignore
            return [label_to_pos[k] for k in key] # type: ignore

A FAM might implement that lookup and return an array of integers more efficiently than what is done above.

This probably needs a new interface, like get_many().

This can pre-size the returned container, potentially making it more efficient. It is not clear if an array or list would give better performance.