[3.6] bpo-28556: Update to typing: treat subscripted generics as proxies (GH-265) (GH-268)

(cherry picked from commit abb3b8ad94d699c8560d94ee9bac9c917b382abe)
(cherry picked from commit 365cb5bb9069273e6970c9d5d17ee2fe5003e7ac)
2 files changed