Add material API to python

UDN ask to control mesh materials in python script. The API is public but not expose.

I suggest to add functionalities to the editor scripting utilities plugin for both static and skeletal meshes.

see:

• \Engine\Plugins\Editor\EditorScriptingUtilities\Source\EditorScriptingUtilities\Public\EditorStaticMeshLibrary.h
• E:\P4\Release-4.24\Engine\Plugins\Editor\EditorScriptingUtilities\Source\EditorScriptingUtilities\Public\EditorSkeletalMeshLibrary.h

Try to query or assign static mesh material slot information in python

Make sure it work also for skeletal mesh