[3.12] gh-104614: Make Sure ob_type is Always Set Correctly by PyType_Ready() (gh-105122) (gh-105211)

When I added the relevant condition to type_ready_set_bases() in gh-103912, I had missed that the function also sets tp_base and ob_type (if necessary).  That led to problems for third-party static types.

We fix that here, by making those extra operations distinct and by adjusting the condition to be more specific.
(cherry picked from commit 1469393)

Co-authored-by: Eric Snow ericsnowcurrently@gmail.com