runtime: Add TODO for mp_resume() on handling .close().
Exceptions in .close() should be ignored (dumped to sys.stderr, not propagated), but in uPy, they are propagated. Fix would require nlr-wrapping .close() call, which is expensive. Bu on the other hand, .close() is not called often, so maybe that's not too bad (depends, if it's finally called and that causes stack overflow, there's nothing good in that). And yet on another hand, .close() can be implemented to catch exceptions on its side, and that should be the right choice.