Improve fixtures for builtins.type and types.UnionType (#17400)

In typeshed `builtins.type` is not generic, so it shouldn't be generic
in fixtures either.

Also replace `types.Union` with `types.UnionType` in test stubs, as the
former doesn't exist.

test-data/unit/check-classes.test

@@ -3466,7 +3466,7 @@ def foo(arg: Type[Any]):
 from typing import Type, Any
 def foo(arg: Type[Any]):
     reveal_type(arg.__str__)  # N: Revealed type is "def () -> builtins.str"
-    reveal_type(arg.mro())  # N: Revealed type is "builtins.list[builtins.type[Any]]"
+    reveal_type(arg.mro())  # N: Revealed type is "builtins.list[builtins.type]"
 [builtins fixtures/type.pyi]
 [out]
 

test-data/unit/fixtures/isinstance.pyi

@@ -5,7 +5,7 @@ T = TypeVar('T')
 class object:
     def __init__(self) -> None: pass
 
-class type(Generic[T]):
+class type:
     def __init__(self, x) -> None: pass
     def __or__(self, other: type) -> type: pass
 

test-data/unit/fixtures/isinstance_python3_10.pyi

@@ -7,15 +7,15 @@ T = TypeVar('T')
 class object:
     def __init__(self) -> None: pass
 
-class type(Generic[T]):
+class type:
     def __init__(self, x) -> None: pass
-    def __or__(self, x) -> types.Union: pass
+    def __or__(self, x) -> types.UnionType: pass
 
 class tuple(Generic[T]): pass
 
 class function: pass
 
-def isinstance(x: object, t: Union[Type[object], Tuple[Type[object], ...], types.Union]) -> bool: pass
+def isinstance(x: object, t: Union[Type[object], Tuple[Type[object], ...], types.UnionType]) -> bool: pass
 def issubclass(x: object, t: Union[Type[object], Tuple[Type[object], ...]]) -> bool: pass
 
 class int:

test-data/unit/fixtures/type.pyi

@@ -13,7 +13,7 @@ class object:
 
 class list(Generic[T]): pass
 
-class type(Generic[T]):
+class type:
     __name__: str
     def __call__(self, *args: Any, **kwargs: Any) -> Any: pass
     def __or__(self, other: Union[type, None]) -> type: pass

test-data/unit/lib-stub/types.pyi

@@ -12,11 +12,8 @@ class ModuleType:
 class GenericAlias: ...
 
 if sys.version_info >= (3, 10):
-    class Union:
-        def __or__(self, x) -> Union: ...
-
     class NoneType:
         ...
 
     class UnionType:
-        ...
+        def __or__(self, x) -> UnionType: ...