gh-103763: Implement PEP 695 (#103764)

This implements PEP 695, Type Parameter Syntax. It adds support for:

- Generic functions (def func[T](): ...)
- Generic classes (class X[T](): ...)
- Type aliases (type X = ...)
- New scoping when the new syntax is used within a class body
- Compiler and interpreter changes to support the new syntax and scoping rules 

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
Co-authored-by: Eric Traut <eric@traut.com>
Co-authored-by: Larry Hastings <larry@hastings.org>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Objects/unionobject.c

@@ -147,10 +147,14 @@ get_types(PyObject **obj, Py_ssize_t *size)
 static int
 is_unionable(PyObject *obj)
 {
-    return (obj == Py_None ||
+    if (obj == Py_None ||
         PyType_Check(obj) ||
         _PyGenericAlias_Check(obj) ||
-        _PyUnion_Check(obj));
+        _PyUnion_Check(obj)) {
+        return 1;
+    }
+    PyInterpreterState *interp = PyInterpreterState_Get();
+    return Py_IS_TYPE(obj, interp->cached_objects.typealias_type);
 }
 
 PyObject *