[Core] Move dynamic macro "stop recording" logic to a function (#21108)

quantum/process_keycode/process_dynamic_macro.h

@@ -39,3 +39,4 @@ void dynamic_macro_record_start_user(int8_t direction);
 void dynamic_macro_play_user(int8_t direction);
 void dynamic_macro_record_key_user(int8_t direction, keyrecord_t *record);
 void dynamic_macro_record_end_user(int8_t direction);
+void dynamic_macro_stop_recording(void);