refactor: Change simulator state detection logic to use faster APIs

[mykola-mokhnach]

The stat method internally invokes simctl list, which could be pretty slow, especially if multiple simulators are installed on the system. I've switched the state detection API to use getenv call as a workaround. In opposite to the list call it only queries single simulator, which makes the overall performance better. On my machine the timings were:

$ time xcrun simctl getenv 0B2C9CE6-29AC-4494-B64F-CE711619146E dummy
...
xcrun simctl getenv 0B2C9CE6-29AC-4494-B64F-CE711619146E dummy  0.08s user 0.09s system 88% cpu 0.184 total

$ % time xcrun simctl list
....
xcrun simctl list  0.11s user 0.20s system 43% cpu 0.723 total

[mykola-mokhnach]

cc @sauce-tartar

[KazuCocoa]

Nice to find it.
I also measured the performance on my machine (same result)