Remove GfxCoreHelper unused methods. Move test-specific types to test sources.
1) computeSlmValues: is not used in other places than tests. Remove it
and unify tests placement
2) isForceDefaultRCSEngineWARequired, unTypedDataPortCacheFlushRequired,
getMaxPtssIndex: unused, remove
3) DwordBuilder: only used in tests, remove it by tests refactoring
Signed-off-by: Naklicki, Mateusz <mateusz.naklicki@intel.com>