Testing: split input test (#2762)

test(pointing): Add mock input device.

New mock input device to generate input events for tests.

test(split): Add peripheral input test.

Test event propagation from peripheral input devices.

fix(split): Proper scoping for local within switch.

Minor compile fix.

chore: Fix up test snapshots after logging changes.

Adjust the test snapshots after logging changes to the central.

fix(kscan): Don't fire last mock event twice.

Fix a bug where the kscan mock would raise the last mock event
twice before halting processing.

app/tests/ble/split/peripheral-input/shared.dtsi

@@ -0,0 +1,16 @@
+/ {
+    splits {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        split_input: split_input@0 {
+            compatible = "zmk,input-split";
+            reg = <0>;
+        };
+    };
+
+    split_listener: split_listener {
+        compatible =  "zmk,input-listener";
+        status = "disabled";
+        device = <&split_input>;
+    };
+};