[clang] [llvm] [coro] Lower `llvm.coro.await.suspend.handle` to resume with tail call (PR #89751)

[via cfe-commits]

zmodem wrote:

What do you think?

(The test updates are a bit hacky for now, but I wanted to get feedback before spending more time on them. Also I think many of the tests become uninteresting after this patch and could probably be deleted.)

https://github.com/llvm/llvm-project/pull/89751