coroutines: Update tests for get-return-object errors.

coroutines: Update tests for get-return-object errors.

We updated the handling of the errors for cases when the
ramp return cannot be constructed from the user's provided
get-return-object method.  This updates the testcases to
cover this.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/void-gro-non-class-coro.C: Moved to...
	* g++.dg/coroutines/coro-bad-gro-01-void-gro-non-class-coro.C: ...here.
	* g++.dg/coroutines/coro-bad-gro-00-class-gro-scalar-return.C: New test.