Summary:
With the new design from vpileggi, this diff separated a new app UI to the current one.
This diffs show the toggle switch to enable Sandy UI for devs who are in `flipper_sandy` GK. When toggled, it will bring Sandy UI up.
Reviewed By: mweststrate
Differential Revision: D23599398
fbshipit-source-id: d85c707e0fe7726a418b3551cedb36e455fb7d14