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

Parameters to a coroutine get copied (moved) to coroutine-local
instances which code inside the coroutine then uses.

The original parameters should not be part of the frame. Normally
CoroSplit figures that out by itself, but for [[clang::trivial_abi]]
parameters which, get destructed at the end of the ramp function, it
does not (see bug), causing use-after-free's if the frame is destroyed
before the end of the ramp (as happens if it doesn't suspend).

Since Clang knows these should never be part of the frame, use metadata
to make it so.

Fixes #127499

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