[libc++] Remove <experimental/coroutine>

We've been shipping <coroutine> since LLVM 14, so LLVM 17 won't ship
the <experimental/coroutine> header per our policy for removing TSes.

Differential Revision: https://reviews.llvm.org/D108697

NOKEYCHECK=True
GitOrigin-RevId: 226c444b3882e085daf7c9f8e284cfad44838e32
53 files changed