Enhance further testcases to verify handling of OpenACC privatization level [PR90115]

Enhance further testcases to verify handling of OpenACC privatization level [PR90115]

As originally introduced in commit 11b8286a83289f5b54e813f14ff56d730c3f3185
"[OpenACC privatization] Largely extend diagnostics and corresponding testsuite
coverage [PR90115]".

	PR middle-end/90115
	gcc/testsuite/
	* c-c++-common/goacc-gomp/nesting-1.c: Enhance.
	* gfortran.dg/goacc/common-block-3.f90: Likewise.
	libgomp/
	* testsuite/libgomp.oacc-c-c++-common/acc_prof-kernels-1.c: Enhance.
	* testsuite/libgomp.oacc-fortran/if-1.f90: Likewise.