Update combined brightness slider/keyboard control state for Apple screens when brightness is changed outside of the app

[waydabber]

When combined brightness control is enabled, system level (ambient sensor, touchbar, mission control) panel brightness changes are not reflected in the current state - this results in an unexpected brightness change when the user adjusts the brightness via keyboard or slider.

[waydabber]

This is a rather tricky problem as combined brightness will (or can) involve both sub-zero-hardware dimming and above-max-hardware XDR upscale for Apple screens so there must be some kind of tradeoff. Apple brightness levels will only replicate to the combined sliders if the slider is inside the minimum and maximum hardware level range (this is currently 20%->100% for Apple displays).

[waydabber]

I built an elaborate logic to handle this. Obviously macOS scales will influence hardware brightness only, this is properly replicated to the combined hardware brightness slider, if needed software adjustments and upscaling also gradually moves to the appropriate level so the resulting experience is a quite smooth one.