Further improve Fortran column location information [PR92793]

Further improve Fortran column location information [PR92793]

Building on top of commit 9c81750c5bedd7883182ee2684a012c6210ebe1d "Fortran] PR
92793 - fix column used for error diagnostic", there is another place where we
have to use 'gfc_get_location' returning column-corrected locations.

For example, this improves column location information for OMP constructs.

	gcc/fortran/
	PR fortran/92793
	* trans.c (gfc_set_backend_locus): Use 'gfc_get_location'.
	(gfc_restore_backend_locus): Adjust.
	gcc/testsuite/
	PR fortran/92793
	* gfortran.dg/goacc/pr92793-1.f90: Adjust.

(cherry picked from commit 5677444f7e7ca15557030902c3d09dab4852fa90)