* Add dedicated init priority for the sideband kscan.
* Refactor sideband code for clarity.
* Tweaks to direct kscan for clarity.
* Make sideband behavior row optional for brevity.
* Allow overriding ZMK Uno sideband behaviors.
* Instead of gpio key behavior trigger, add new kscan driver that
decorates/wraps a given kscan driver and will invoke basic system
behavior assigned to a given row + column, without the need for keymap
mapping in the matrix transform, bypassing keymaps entirely.