Working: A proper countdown to idle works and is cancelled on resume.
Displays are dimmed if possible at countdown start and restorted at
resume. The screens properly lock. The power to the displays is turned
off. The power is restore upon first resume. Layout and brightness
restored on unlock.
Known issue: Displays are not restored if the system idles again while
on lock screen. This shouldn't really happen and is a possible indicator
of tampering, which is kind of cool, but it's janky. Power needs to be
restored with the toggle_displays hotkey.