rembert type annotations and dependencies
Added type annotations to Rembert per the guidelines. Modified Bert where copied from transformers.models.bert.modeling_bert

#16059 

@Rocketknight1 

_The documentation is not available anymore as the PR was closed or merged._<|||||>@Rocketknight1 Any idea on why this is failing?
Only made modifications to Bert and Rembert, with copies to the other seven models based on make fix-copies.
Model template seems to fail due to a bad import of Optional, from what I can tell.<|||||>@jacobdineen Thanks for this! I would guess that `make fix-copies` has copied code to the other models, but one or more of the files it copied to hasn't imported `Optional`, and so the code crashes there. If you add the missing imports to those files it should work!

Also, some of the return types here seem to be missing bits - they're just `Union[Tuple]` but usually there's another return type as well in the union.