* In order to be sure the rest of the system is fully ready before
intializing, because init may result in immediate events being
triggered when used with toggle direct kscan inner devices.
* 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.
