Implemented uniform API in Viewport class to override 2D and/or
3D camera.

Added buttons in 2D and 3D editor viewport toolbars that override
the running game camera transform with the editor viewport camera
transform. Implemented via remote debugger protocol and camera
override API.

Removed LiveEditFuncs function pointers from ScriptDebugger class.
Since the debugger got access to the SceneTree instance (if one
exists), there is no need to store the function pointers. The live
edit functions in SceneTree are used directly instead. Also removed
the static version of live edit functions in SceneTree for the same
reason. This reduced the SceneTree -> Debugger coupling too since
the function pointers don't need to be set from SceneTree anymore.

Moved script_debugger_remote.h/cpp from 'core/' to 'scene/debugger/'.
This is because the remote debugger is now using SceneTree directly
and 'core/' classes should not depend on 'scene/' classes.