Add option to opt-out a display from "disconnect built-in display when an external display is connected"

[waydabber]

Discussed in #3794

^{Originally posted by liuzhcn December 15, 2024}
I have only one external monitor in my office, which I use together with the built-in display. However, at home, I have two external monitors, and the built-in display is no longer used. I have created two groups: ‘office’ and ‘home’. I hope that when the laptop connects to two external monitors at home (via a Thunderbolt 3 dock), it will automatically turn off the built-in display, while in the office, the built-in display remains on. Currently, it seems impossible to achieve this:
1. If the built-in display is set to turn off when an external monitor is connected, the built-in display will be turned off in both scenarios.
2. If the display is set to automatically turn off, it will remain in its last state (if off, it stays off).
3. If I manually turn it off, the situation is the same as point 2.

[waydabber]

I am not sure @liuzhcn whether it is a good idea to tie this to display groups as the presence and connected state of a display might influence the activation of a display group and it is very easy to get into some sort of cycle.

I will add an option instead for external displays to opt out-of the auto-disconnect feature. With this change you should be able to specify one or more external display that does not trigger the auto-disconnect feature. This should be a simple and effective solution.

[waydabber]