Fixes #8650

Summary of Changes

Set the flight number in the FMC and the ATSU regardless of whether it's already taken. This has the benefit of setting the flight number instantly, instead of waiting to hear back from the API. The check is still made, and if the flight number is taken, the FLT NBR IN USE message is received and displayed by the ATSU.

Not yet tested: the effect of having a duplicate flight number during TELEX operations.

Screenshots (if necessary)

Starting the init req from the FCU. Note that no message is displayed in the FCU. A received message can be seen in the ATSU. The FLT NBR IN USE message is in the scratchpad, and the flight number is populated in the AOC.

I don't know if this is expected, but starting the request from the ATSU does not populate anything in the FCU, unlike the reverse.

Not necessarily related to this PR, but since it was brought up, I can confirm that the ATSU is reset completely after a flight is completed, including the flight number.

References

Additional context

Discord username (if different from GitHub):

Testing instructions

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