Clean-Up unused code related to GMock

This commit:
- Removes usings e.g. ::testing::Return
- Removes unnecessary gmock inclues
- Replaces Gmock macros (e.g. EXPECT_THAT) with our custom implementations

Related-To: NEO-4941
Signed-off-by: Fabian Zwolinski <fabian.zwolinski@intel.com>

opencl/test/unit_test/gen9/skl/linux/hw_info_config_tests_skl.cpp

@@ -5,7 +5,8 @@
  *
  */
 
-#include "opencl/test/unit_test/helpers/gtest_helpers.h"
+#include "shared/test/unit_test/helpers/gtest_helpers.h"
+
 #include "opencl/test/unit_test/os_interface/linux/hw_info_config_linux_tests.h"
 
 using namespace NEO;