Log flight number in flash metadata and use it for the flight ID

- We can put the flight number in the flash chip in the metadata sector, so the flight IDs can just be the flight number instead of randomly generated numbers.
- Using the flight number makes it easier when decoding the flash chip to track which data belongs to which flight.
- Flight numbers are ordinal while the random flight IDs aren't, so you can't tell which one came first or later.