testsuite, coroutines : Mark final awaiters and co_await operators noexcept.

testsuite, coroutines : Mark final awaiters and co_await operators noexcept.

This is part of the requirement of [dcl.fct.def.coroutine]/15.

In addition to promise final_suspend() calls, the following cases must
also be noexcept as per discussion in PR95616.

- finalSuspendObj.operator co_await()
- finalSuspendAwaiter.await_ready()
- finalSuspendAwaiter.await_suspend()
- finalSuspendAwaiter.await_resume()
- finalSuspedObj destructor
- finalSuspendAwaiter destructor

Fixed for missing cases in the testsuite as a prerequisite to fixing
PR95616.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/pr94879-folly-1.C: Make final suspend
	expression components noexcept.
	* g++.dg/coroutines/pr94883-folly-2.C: Likewise.
	* g++.dg/coroutines/pr95345.C: Likewise.