coroutines: Add a cleanup expression for g-r-o when needed [PR95477].

coroutines: Add a cleanup expression for g-r-o when needed [PR95477].

The PR reports that we fail to destroy the object initially created from
the get-return-object call.  Fixed by adding a cleanup when the DTOR is
non-trivial.  In addition, to meet the specific wording that the call to
get_return_object creates the glvalue for the return, we must construct
that in-place in the return object to avoid a second copy/move CTOR.

gcc/cp/ChangeLog:

	PR c++/95477
	* coroutines.cc (morph_fn_to_coro): Apply a cleanup to
	the get return object when the DTOR is non-trivial.

gcc/testsuite/ChangeLog:

	PR c++/95477
	* g++.dg/coroutines/pr95477.C: New test.
	* g++.dg/coroutines/void-gro-non-class-coro.C: New test.