bpo-45438: format of inspect.Signature with generic builtins (GH-29212)

Use types.GenericAlias in inspect.formatannotation to correctly add
type arguments of builtin types to the string representation of
Signatures.

Co-authored-by: Martin Rückl <martin.rueckl@codecentric.de>
(cherry picked from commit d02ffd1b5c0fd8dec6dd2f7e3f2b0cfae48b7899)

Co-authored-by: Martin Rueckl <enigma@nbubu.de>