[rocprofiler-systems] Implement GTest/GMock integration for unit testing (#1777)

* googletest project set up

---------

Co-authored-by: Aleksandar Djordjevic <adjordje@amd.com>
Co-authored-by: Milan Radosavljevic <milan.radosavljevic@amd.com>

.gitmodules

@@ -82,3 +82,6 @@
 [submodule "projects/rocprofiler-systems/examples/openmp/external/ompvv"]
 	path = projects/rocprofiler-systems/examples/openmp/external/ompvv
 	url = https://github.com/OpenMP-Validation-and-Verification/OpenMP_VV.git
+[submodule "projects/rocprofiler-systems/external/googletest"]
+	path = projects/rocprofiler-systems/external/googletest
+	url = https://github.com/google/googletest.git