Shader hot compile and reload

[roeas]

Finally, we can modify the shader and apply the changes in real time while the editor is launched.

• The compilation of shader occurs when the editor window regains focus, so make sure that the syntax in shader is correct at this time.
• The watching directory is CatDogEngine/Engine/BuiltInShaders/shaders.
• No support for detecting changes in shader header files.

TODO: We can't handle dependencies between resource files right now.

[T-rvw]

It is a very useful feature for us to improve experience on developing shaders across platforms.