Introduce 3rd idle inhibitor state: when inhibited from somewhere else

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Currently the idle inhibitor can only be activated or deactivated. Different styles can be applied for the different states to visually represent the current state.

Some programs can inhibit idle on their own, e.g. a video player. Further it is possible to configure certain conditions that inhibit idle, e.g. for sway see inhibit_idle: https://man.archlinux.org/man/sway.5

I would like the segment to support this as a 3rd state, e.g. external so that I can see at a glance if I stand up now, is it deactivated, activated externally by some program or configuration, or activated. Additionally if externally activated it would be nice to be able to see what causes it e.g. in the tooltip. This info can be obtained e.g. with swaymsg -t get_tree to get a hierarchical representation of all windows and searching for one where inhibit_idle is true (however there may be better ways to do it).