Utility function to remove all arguments of an `argparse.ArgumentParser` from `PETSc.Options()`

[JHopeCollins]

This would mean that the output of -options_left wouldn't be polluted by any command line arguments meant for argparse.

CW: single dispatch free function? Base implementation for an Iterable of strings, and specialisations e.g. for argparse which turn an argparse.Formatter into a list of strings to recurse