Extend default recording of images/poses to all vehicles in a scene

[saihv]

The currently default recording code (record button in-game, or key R) only records images and position/orientation data for the first vehicle in the game. This PR extends that functionality to all vehicles, by dealing with the full list of vehicle APIs (VehicleSimApiBase objects) rather than just one. For n vehicles in a scene, recording n images and n poses in airsim_rec.txt is treated as one step.

Note: This has only been tested on drones for up to five vehicles.

[sytelus]

Thanks. This is good change but extensive as well. I'll go through this early next week.

[saihv]

Just a quick note from my testing: it looks like having multiple vehicles recording simultaneously is causing AirSim to be more prone to the Game <-> Recording thread deadlock issue mentioned in #1694. Utilizing the fix provided in the related PR: #1695 seems to fix the problem for the multi vehicle recording case as well.

FYI, if it's helpful in any way: extending the recording to multiple vehicles does not cause the deadlock problem in v1.2.0 (Windows), only in the latest versions.

[zhuboshun2015]

@saihv Could you give more details about how to achieve this ? I have modified the code(Extend default recording of images/poses to all vehicles) as you upload,

but next step is ?

[zhuboshun2015]

谢谢。这是一个很好的改变，但也很广泛。下周初我会经历这个。

Hello ! Did you achieve that?

[saihv]

@zhuboshun2015 If you've already adapted these changes into your code, all you'd have to do is press 'R' as you usually would, and images/poses from all drones will be recorded.

[zhuboshun2015]

@saihv Yes, I did.But when I look at the.txt file, it seems that there is only the position and posture information of drone1.I don't know if I have to set 'settings.json'? This is my settings.json document.
settings.txt

[zhuboshun2015]

@saihv thank you ! I have success in doing this . But it is a little difficult to recognize every drone's number.How do you recognize this ?