Add overloads for `argparse.ArgumentParser.parse_x_args()`

An extension of #2566, seems like the typings for parse_known_args, parse_intermixed_args, parse_known_intermixed_args (and the undocumented _parse_known_args) of argparse.ArgumentParser were overlooked, as they all share the same pattern as parse_args for typing the namespace class.

定位 argparse.ArgumentParser 的存根，并将现有的 parse_args 重载与 parse_known_args、parse_intermixed_args、parse_known_intermixed_args 和 _parse_known_args 进行比较。为列出的各个方法添加相匹配的 namespace 类重载；当它们的类型标注遵循与 parse_args 相同的模式时，即表示完成。