[clang] [Coroutines] Mark parameter allocas with coro.outside.frame metadata (PR #127653)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Adding metadata to an instruction should never be required for correctness: optimizations are not required to preserve metadata on instructions, so this "fix" will just break again later.

If we need two different kinds of alloca in coroutine functions, we need a different way to identify them.

https://github.com/llvm/llvm-project/pull/127653