refactor: Add kscan sideband behavior driver

* 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.

app/Kconfig

@@ -512,6 +512,12 @@ config ZMK_KSCAN_EVENT_QUEUE_SIZE
 
 endif # ZMK_KSCAN
 
+config ZMK_KSCAN_SIDEBAND_BEHAVIORS
+    bool
+    default y
+    depends on DT_HAS_ZMK_KSCAN_SIDEBAND_BEHAVIORS_ENABLED
+    select KSCAN
+
 menu "Logging"
 
 config ZMK_LOGGING_MINIMAL