systemd: Set up a watchdog

Allows to notify systemd whether kwin is still running and possibly restart the service if it stops responding.

Use Type=notify-reload to watch the kwin service. This will make it so we receive SIGHUP rather than SIGTERM on the wrapper which we can handle gracefully and stop the kwin process and restart as expected.

https://www.freedesktop.org/software/systemd/man/latest/systemd.service.html

Signed-off-by: Victoria Fischer victoria.fischer@mbition.io

Draft because it was reverted as of !5104 (merged)

Dropped the draft because it works for Vlad now. I think the problem was that some linkers wouldn't do the Q_COREAPP_STARTUP_FUNCTION from a static library. I've also extended the timeout.