feat(color): widget app mode

[philmoz]

Fixes #4371 & #2629

Rework the way 'full screen' mode is selected for widgets.

It uses the 'EdgeTX' button in the top left to differentiate mode - at the moment I need this to have a way to open the quick menu (tapping on the widget will not work).

'App mode' is enabled by creating a layout with 1 widget (the 'full screen' layout) and turning off the topbar, flight modes, sliders and trims.

• The default 'app mode' view would be the selected widget (full screen); but also still showing the EdgeTX button in the top left corner (visual indicator of mode). Keys and touch events are not passed to the widget. Swiping can be used to change view and enter/touch brings up quick menu.
• A long ENTER press or long touch on the screen hides the EdgeTX button and directs key and touch events to the widget. The user will not be able to swipe to change views, or open the quick menu.
• A long press of RTN key shows the EdgeTX button and stops events/touch going to the widget.

TODO:

• Rename 'Full screen' text to 'App mode'
• Add 'App mode' control/toggle the screen setup page