MAGIC value for powerReason should be stored in RTC backup on Horus (#7096)

- Allows the radio main application to start correctly when coming from an app in RAM
- Refactoring of the `UNEXPECTED_SHUTDOWN()` process
- Saves the RTC battery as BACKUP RAM is not needed on normal shutdown
- On PWR OFF on an ALERT, the radio won't show the next alert before shutting down
- Bootloader flashable through the SD Manager

radio/src/storage/eeprom_rlc.cpp

@@ -729,7 +729,7 @@ void RlcFile::nextRlcWriteStep()
 void RlcFile::flush()
 {
   while (!eepromIsTransferComplete())
-    wdt_reset();
+    WDG_RESET();
 
   ENABLE_SYNC_WRITE(true);