This is convenient when components need only to parse a subset of an
application's arguments, and can be implemented with minor changes to
_parse_args: basically just add unknown arguments to a list instead of
raising an exception.
CPython's argparse needs around 160k heap just for the module, and has
heaps of dependencies. This minimal version can run in 16k heap and has
only sys and namedtuple dependencies (which are builtin to MicroPython).