Support AIR ADT simulator argument in launch.json

From Daniel Sperl:

> ... as for the icing on the cake, or if you're looking for ideas for a future update (haha), one small but useful addition would be to add a property that allows choosing the device to be simulated. Harman recently added the simulator parameter to adt recently, to be used like this: -simulator "iPhone 8". That way, one wouldn't need to rely on the environment variable any longer.

> But, again, that's just a small nice-to-have idea for the future – it's FANTASTIC to be able to run the simulator like that, as it is. Thanks again! 😁

Source: https://github.com/BowlerHatLLC/vscode-swf-debug/issues/30#issuecomment-883249004

Start by tracing how launch.json settings reach the AIR ADT invocation. Add support for selecting a simulator through the requested property and the `-simulator "iPhone 8"` argument, while preserving the existing environment-variable behavior. Done means a configured simulator is passed to ADT and configurations without it still work.

Written by the indexing model from the issue text.