Support passing values through decorators from factories

This builds on the approach taken in https://github.com/davidhalter/jedi/pull/1613
but applies it to type vars themselves so that their type var
nature is preserved when a function returns Callable[[T], T] and
the T has an upper bound.

test/completion/pep0484_generic_passthroughs.py

@@ -250,6 +250,28 @@ is_decorated_by_class_decorator_factory(the_par
 )
 
 
+def decorator_factory_plain() -> Callable[[T], T]:
+    pass
+
+#? Callable()
+decorator_factory_plain()
+
+#?
+decorator_factory_plain()()
+
+#? int()
+decorator_factory_plain()(42)
+
+is_decorated_by_plain_factory = decorator_factory_plain()(will_be_decorated)
+
+#? will_be_decorated
+is_decorated_by_plain_factory
+
+#? ['the_param=']
+is_decorated_by_plain_factory(the_par
+)
+
+
 class class_decorator_factory_bound_callable:
     def __call__(self, func: TCallable) -> TCallable:
         ...
@@ -270,6 +292,25 @@ is_decorated_by_class_bound_factory(the_par
 )
 
 
+def decorator_factory_bound_callable() -> Callable[[TCallable], TCallable]:
+    pass
+
+#? Callable()
+decorator_factory_bound_callable()
+
+#? Callable()
+decorator_factory_bound_callable()()
+
+is_decorated_by_bound_factory = decorator_factory_bound_callable()(will_be_decorated)
+
+#? will_be_decorated
+is_decorated_by_bound_factory
+
+#? ['the_param=']
+is_decorated_by_bound_factory(the_par
+)
+
+
 class That(Generic[T]):
     def __init__(self, items: List[Tuple[str, T]]) -> None:
         pass