Improve typing of use_state hook

[mofojed]

We want the typings of use_state to match the behaviour of React.useState.
In particular, if you want to define an optional number value, you should be able to define it simply as:

x, set_x = use_state[int]()
# x should be type `int | None`

This will require python 3.12, for the type parameter syntax: https://docs.python.org/3/reference/compound_stmts.html#type-params

Also see discussion about applying default values with overloads: python/mypy#3737 (comment)