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/module/drivers/input/CMakeLists.txt

@@ -0,0 +1,6 @@
+# Copyright (c) 2020-2023 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+zephyr_library_amend()
+
+zephyr_library_sources_ifdef(CONFIG_ZMK_INPUT_MOCK input_mock.c)