Add @type_check_only to various typeshed-only procotols in stdlib (#14465)

Mark various typeshed-only protocols as `@type_check_only` in stdlib

stdlib/contextlib.pyi

@@ -4,7 +4,7 @@ from _typeshed import FileDescriptorOrPath, Unused
 from abc import ABC, abstractmethod
 from collections.abc import AsyncGenerator, AsyncIterator, Awaitable, Callable, Generator, Iterator
 from types import TracebackType
-from typing import IO, Any, Generic, Protocol, TypeVar, overload, runtime_checkable
+from typing import IO, Any, Generic, Protocol, TypeVar, overload, runtime_checkable, type_check_only
 from typing_extensions import ParamSpec, Self, TypeAlias
 
 __all__ = [
@@ -112,7 +112,7 @@ else:
         ) -> bool | None: ...
 
 def asynccontextmanager(func: Callable[_P, AsyncIterator[_T_co]]) -> Callable[_P, _AsyncGeneratorContextManager[_T_co]]: ...
-
+@type_check_only
 class _SupportsClose(Protocol):
     def close(self) -> object: ...
 
@@ -123,6 +123,7 @@ class closing(AbstractContextManager[_SupportsCloseT, None]):
     def __exit__(self, *exc_info: Unused) -> None: ...
 
 if sys.version_info >= (3, 10):
+    @type_check_only
     class _SupportsAclose(Protocol):
         def aclose(self) -> Awaitable[object]: ...