Fix run and rpc type annotations and run with function pointer

[dfarr]

The type annotations of run and rpc had regressed to return type Handle[Generator[Any, Any, T] | T as opposed to just type T.

This PR fixes this and adds more robust "tests" (implemented as unit tests, checked by pyright) to help mitigate regressions in the future. In addition we are now wrapping the underlying function using functools.update_wrapper and binding the identity of the Function instance to the function itself.

Note:

Ideally, run and rpc would not require special type annotations to work with Function (since this class implements the __call__ method and is therefore callable). As best I can tell this is required because the python type system lacks conditional types, therefore the __call__ method is implemented as:

def __call__(self, ctx: Context, *args: P.args, **kwargs: P.kwargs) -> Generator[Any, Any, R] | R:
    return self._func(ctx, *args, **kwargs)

Which is not equivalent to Generator[Any, Any, R] and R respectively and likely the reason for the regression. If ever python adds conditional types, or we figure out a better way to implement Function we can likely remove these annotations (and switch Function run/rpc to use self._func which preserves type information) in the future.