kcm: Add checkbox to disable DDC/CI for a given output

Companion MR for libraries/plasma-wayland-protocols!98 (merged) and related MRs linked from there.

Requires updates to plasma-wayland-protocols and libkscreen to build, as well as updates to kwin and powerdevil to work as intended.

Some monitors have buggy DDC/CI implementations, or the user may want to disable it for other reasons. Allow them to do so and use KWin's software brightness controls instead.

In the future, this toggle may also affect contrast settings, input source selection, or any other useful DDC/CI features.

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