Summary:
I noticed that Android device detection is _much_ faster than iOS, so I tried to optimize it a bit
1. Removed a test run on `instruments -s`. That command is really slow (easily 5 secs), and the check has become redundant since Doctor already does a similar check
2. When querying for devices, it tries to fetch emulated and physical devices in parallel, but only processes the results after both have finished. However, finding simulators is almost instant, while querying the physical devices takes ~5 seconds ore more. So in this diff we process the found devices till in parallel, rather than waiting until both have arrived
This diff reduces the time until the ios simulator + FB app is detected from 28 to 4 seconds on my machine.
Changelog: Improved the startup sequence for emulated iOS devices, so that devices and apps connect a lot faster after starting Flipper
Reviewed By: jknoxville
Differential Revision: D21907597
fbshipit-source-id: 73edf0b04c4ad8367e04557e33f4c0d9e9bcd710
b94e426261