refactor: replace filename hyphens with underscores

Aligns *.h and *.c to underscore naming convention.

These were kept (with warnings) for backwards compatibility with external boards/shields:
- kscan-mock.h
- matrix-transform.h
They should be removed in the future.

PR: #523

app/src/events/activity_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/activity-state-changed.h>
+#include <zmk/events/activity_state_changed.h>
 
 ZMK_EVENT_IMPL(activity_state_changed);

app/src/events/battery_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/battery-state-changed.h>
+#include <zmk/events/battery_state_changed.h>
 
 ZMK_EVENT_IMPL(battery_state_changed);

app/src/events/ble_active_profile_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/ble-active-profile-changed.h>
+#include <zmk/events/ble_active_profile_changed.h>
 
 ZMK_EVENT_IMPL(ble_active_profile_changed);

app/src/events/keycode_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/keycode-state-changed.h>
+#include <zmk/events/keycode_state_changed.h>
 
 ZMK_EVENT_IMPL(keycode_state_changed);

app/src/events/layer_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/layer-state-changed.h>
+#include <zmk/events/layer_state_changed.h>
 
 ZMK_EVENT_IMPL(layer_state_changed);

app/src/events/modifiers_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/modifiers-state-changed.h>
+#include <zmk/events/modifiers_state_changed.h>
 
 ZMK_EVENT_IMPL(modifiers_state_changed);

app/src/events/position_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/position-state-changed.h>
+#include <zmk/events/position_state_changed.h>
 
 ZMK_EVENT_IMPL(position_state_changed);

app/src/events/sensor_event.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/sensor-event.h>
+#include <zmk/events/sensor_event.h>
 
 ZMK_EVENT_IMPL(sensor_event);

app/src/events/usb_conn_state_changed.c

@@ -5,6 +5,6 @@
  */
 
 #include <kernel.h>
-#include <zmk/events/usb-conn-state-changed.h>
+#include <zmk/events/usb_conn_state_changed.h>
 
 ZMK_EVENT_IMPL(usb_conn_state_changed);