* Add a dedicated settings reset on start init priority and default
it to lower priority (high number) than default FLASH_INIT_PRIORITY
to be sure flash is initialized before we open the area.
Added a new CONFIG_ZMK_SETTINGS_RESET_ON_START option which enables init
code to call zmk_settings_erase(), and changed the settings_reset shield
to use it instead of CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START, so it now
resets all settings instead of just clearing BLE bonds.
CONFIG_ZMK_BLE_CLEAR_BONDS_ON_START is left in place for now in case
someone still needs it. It may be replaced in the future once we find a
better way to repair a broken split connection.
Added a zmk_settings_erase() function to clear all saved settings. This
does not go through Zephyr's settings subsystem, but instead directly
clears the data from the setting storage backend, so a reboot is needed
for it to take effect.
