Plugin cannot handle parallelism

[abjerstedt]

There are 2 separate problems with this plugin regarding parallelism:

1. This plugin assumes that it is the ONLY instance running on a build machine, and doesn't work for teams using multiple runners on one device (such as self hosted MacMini's or MacPros).

• The cleanup script is hardcoded to kill the first emulator which means inevitable collisions.

2. This plugin doesn't allow for test sharding.

[abjerstedt]

@ychescale9 - To clarify this also means the device matrix logic is broken. You can only run a single device at a time because we are force killing a specific adb instance.

[RTodorov]

I'm also facing this issue when trying to run a matrix of different devices, which I assume is a common use-case for the plugin.