Add @disjoint_base decorator in the stdlib (#14599)

And fix some other new stubtest finds.

stdlib/_interpreters.pyi

@@ -1,7 +1,7 @@
 import types
 from collections.abc import Callable
 from typing import Any, Final, Literal, SupportsIndex, TypeVar, overload
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, disjoint_base
 
 _R = TypeVar("_R")
 
@@ -12,6 +12,7 @@ class InterpreterError(Exception): ...
 class InterpreterNotFoundError(InterpreterError): ...
 class NotShareableError(ValueError): ...
 
+@disjoint_base
 class CrossInterpreterBufferView:
     def __buffer__(self, flags: int, /) -> memoryview: ...