* AutoSuspend: Use the canSuspend devcap check instead of reinventing the wheel.
* Device & UIManager: Cleanup canSuspend devcap check related stuff to avoid boilerplate code.
(It also now defaults to no, and is explicitly set by device implementations where supported).
* AutoSuspend: Re-engage suspend/shutdown timers when fully charged.
This restores the existing behavior pre #9036
(c.f., https://github.com/koreader/koreader/pull/9258#issuecomment-1167672356)
* SDL: Unbreak the fake suspend behavior so that it actually works.
Tweak the default screensaver message to remind users that Power is bound to F2.
(Fix#9262)
* AutoSuspend: Re-engage suspend/shutdown timers on unplug.
This matters on Kobo, because the unexpected wakeup guard might have stopped the suspend timer.