Revert "Simplify lifetime extension for async ObjC calls."
This reverts commit 01d470ce3280c9d04ad32420aae1d9cd4dacaae3.
Just to be safe, I'm reverting this part of https://github.com/apple/swift/pull/41571
as well, until it can be reimplemented in light of issues where a hop
can appear between a get_continuation and an await_continuation
resolves rdar://91502776
