Cinema Path GUI hiding and silhouettes fixes.

Let the JS GUI take care of hiding the GUI and silhouettes and remove the according hardcoding in the engine following rP17594.
Thereby fix some bugs (like not having hid the GUI if there was a message box or different page shown while playing a path) and
fix these two hotkeys broken by rP19375.

Differential Revision: https://code.wildfiregames.com/D631
Fixes #4633
Reviewed By: Vladislav