[OpenACC] Elaborate testcases that verify column location information [PR92793]

After PR92793 commit 9c81750c "Fortran] PR
92793 - fix column used for error diagnostic", commit
d0d0ba20 did "Add tests to verify OpenACC
clause locations", later fixed up in PR92901 commit
e6c90dba to "Fix PR92901: Change test
expectation for C++ in OpenACC test clause-locations.c".

Now, add some more testing to verify/document the status quo.

	gcc/testsuite/
	PR fortran/92793
	* c-c++-common/goacc/clause-locations.c: Rewrite into...
	* c-c++-common/goacc/pr92793-1.c: ... this.
	* gfortran.dg/goacc/clause-locations.f90: Rewrite into...
	* gfortran.dg/goacc/pr92793-1.f90: ... this.