refactor: Fixes for soft-off based on review.

* Better naming for gpio-key behavior triggers.
* Tweaks to scanned behavior trigger to avoid bad semaphore use,
  and reduce chance of issues with slowly scanned matrixes.
* Various code cleanups of style issues.

app/dts/bindings/zmk,gpio-key-wakeup-trigger.yaml

@@ -0,0 +1,18 @@
+# Copyright (c) 2023 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+description: |
+  Driver for a dedicated key for waking the device from sleep
+
+compatible: "zmk,gpio-key-wakeup-trigger"
+
+include: base.yaml
+
+properties:
+  trigger:
+    type: phandle
+    required: true
+    description: The GPIO key that triggers wake via interrupt
+  extra-gpios:
+    type: phandle-array
+    description: Optional set of pins that should be set active before sleeping.