Fix following warnings
1. modules/javafx.graphics/src/main/native-prism-mtl/MetalPipelineManager.m:254:1: warning: method possibly missing a [super dealloc] call [-Wobjc-missing-super-calls]
2. modules/javafx.graphics/src/main/native-prism-mtl/MetalMeshView.m:35:17: warning: method definition for 'getSpecType' not found [-Wincomplete-implementation]
3. modules/javafx.graphics/src/main/native-prism-mtl/MetalContext.m:52:17: warning: method definition for 'setCurrentPipeState:' not found [-Wincomplete-implementation]
4. modules/javafx.graphics/src/main/native-prism-mtl/MetalContext.m:52:17: warning: method definition for 'setCurrentArgumentBuffer:' not found [-Wincomplete-implementation]