Add @final to many unsubclassable stdlib classes (#6299)

stdlib/_thread.pyi

@@ -2,6 +2,7 @@ import sys
 from threading import Thread
 from types import TracebackType
 from typing import Any, Callable, NoReturn, Optional, Tuple, Type
+from typing_extensions import final
 
 error = RuntimeError
 
@@ -9,6 +10,7 @@ def _count() -> int: ...
 
 _dangling: Any
 
+@final
 class LockType:
     def acquire(self, blocking: bool = ..., timeout: float = ...) -> bool: ...
     def release(self) -> None: ...
@@ -29,6 +31,7 @@ TIMEOUT_MAX: float
 
 if sys.version_info >= (3, 8):
     def get_native_id() -> int: ...  # only available on some platforms
+    @final
     class _ExceptHookArgs(Tuple[Type[BaseException], Optional[BaseException], Optional[TracebackType], Optional[Thread]]):
         @property
         def exc_type(self) -> Type[BaseException]: ...