Drop logind integration

[WhyNotHugo]

This integration is unwanted, as expressed in #117.

Additionally, the integration is not quite correct; to properly launch a screen locker before sleeping, swayidle should set a suspend inhibitor at startup, and upon the PrepareForSleep signal, it should start the screen locker and then release the inhibitor lock. The existing implementation is racey and may run the locker after resuming from suspend.

Fixes: https://github.com/swaywm/swayidle/issues/117 Closes: https://github.com/swaywm/swayidle/issues/127 Closes: https://github.com/swaywm/swayidle/issues/121 Closes: https://github.com/swaywm/swayidle/issues/64 Closes: https://github.com/swaywm/swayidle/issues/59 Closes: https://github.com/swaywm/swayidle/pull/125 Closes: https://github.com/swaywm/swayidle/pull/89

[emersion]

Looks good.

A possible replacement for users is https://git.sr.ht/~whynothugo/systemd-lock-handler