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

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

stdlib/copy.pyi

@@ -1,5 +1,5 @@
 import sys
-from typing import Any, Protocol, TypeVar
+from typing import Any, Protocol, TypeVar, type_check_only
 from typing_extensions import Self
 
 __all__ = ["Error", "copy", "deepcopy"]
@@ -7,6 +7,7 @@ __all__ = ["Error", "copy", "deepcopy"]
 _T = TypeVar("_T")
 _SR = TypeVar("_SR", bound=_SupportsReplace)
 
+@type_check_only
 class _SupportsReplace(Protocol):
     # In reality doesn't support args, but there's no other great way to express this.
     def __replace__(self, *args: Any, **kwargs: Any) -> Self: ...