- store the Vulkan descriptor sets in the material - where they belong!

Having them in the base texture object was a major maintenance issue.

src/d_main.cpp

@@ -3401,6 +3401,7 @@ void D_Cleanup()
 	DeinitMenus();
 	LightDefaults.DeleteAndClear();			// this can leak heap memory if it isn't cleared.
 	TexAnim.DeleteAll();
+	TexMan.DeleteAll();
 	
 	// delete DoomStartupInfo data
 	DoomStartupInfo.Name = "";