## Summary
Part of #15383.
As per the spec
(https://typing.python.org/en/latest/spec/overload.html#invalid-overload-definitions):
For `@staticmethod` and `@classmethod`:
> If one overload signature is decorated with `@staticmethod` or
`@classmethod`, all overload signatures must be similarly decorated. The
implementation, if present, must also have a consistent decorator. Type
checkers should report an error if these conditions are not met.
For `@final` and `@override`:
> If a `@final` or `@override` decorator is supplied for a function with
overloads, the decorator should be applied only to the overload
implementation if it is present. If an overload implementation isn’t
present (for example, in a stub file), the `@final` or `@override`
decorator should be applied only to the first overload. Type checkers
should enforce these rules and generate an error when they are violated.
If a `@final` or `@override` decorator follows these rules, a type
checker should treat the decorator as if it is present on all overloads.
## Test Plan
Update existing tests; add snapshots.
7568eeb7a5