Introduce ray tracing shader types

Add following shader types to be parsed properly:
 * RayGenShader
 * AnyHitShader
 * ClosestHitShader
 * MissShader
 * IntersectionShader
 * CallableShader

VK-GL-CTS issue: 2058

Change-Id: If166fa39ffd8692a957e697f7a754428db688845