improvements for hidden types in the sys module

[tungol]

Related to #13016

Access to the various types:

_flags = type(sys.flags),
_float_info = type(sys.float_info),
_hash_info = type(sys.hash_info),
_implementation = type(sys.implementation),
_int_info = type(sys.int_info),
_thread_info = type(sys.thread_info),
_version_info = type(sys.version_info),
_asyncgen_hooks = type(sys.get_asyncgen_hooks()),

[AlexWaygood]

Thanks!

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[AlexWaygood]

Thanks!