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/targets/simu/simpgmspace.cpp

@@ -51,6 +51,7 @@ DMA_TypeDef dma2;
 USART_TypeDef Usart0, Usart1, Usart2, Usart3, Usart4;
 SysTick_Type systick;
 ADC_Common_TypeDef adc;
+RTC_TypeDef rtc;
 #else
 Pio Pioa, Piob, Pioc;
 Pmc pmc;
@@ -672,7 +673,7 @@ void lockFlash()
 {
 }
 
-void flashWrite(uint32_t *address, uint32_t *buffer)
+void flashWrite(uint32_t *address, const uint32_t *buffer)
 {
   simuSleep(100);
 }