allow specifying work/async queues via configuration

[rubu]

Motivation

I need to run idb in a node native addon thus there is nothing to drive the main queue which is used under the hood. This PR seems to allow me to boot a device and receive the callbacks by providing custom async/work queues via FBSimulatorControlConfiguration. I tried to make this an opt in behaviour - the new properties are default nil and have a designated initializer and internally the work/async queues use the old values if these configuration values are not specified.

Test Plan

Testing is something i wanted some feedback on. So obviously:

1. using the existing configuration should not change any tests since as i mentioned this should be opt in
2. tests also use dispatch_get_main_queue() which would then need to be adjusted - as in the tests should then use a given queue (most likely each test should be run with main and with a custom queue?), provide it to the frameworks via the configuration and expect everything to work. Is that the route that should be taken here?

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