[llvm] [Coroutines] Always set the calling convention of generated resuming call from 'llvm.coro.await.suspend.handle' as fast (PR #93167)

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zmodem wrote:

lgtm, thanks!

> We met a regression due to a change of calling convention of this patch.

How did you detect the regression? Was the resume call crashing due to mismatched calling convention? Did the verifier catch it?

https://github.com/llvm/llvm-project/pull/93167