Summary:
This allows us to configure a simulator to use a non-default port pair by using the `defaults` mechanism. For instance, this can be done by running
```
xcrun simctl spawn booted defaults write "Apple Global Domain" "com.facebook.flipper.ports" -string "9088,9089"
```
Reviewed By: lblasa, timur-valiev
Differential Revision: D30731874
fbshipit-source-id: 689d60b1c392f36dceef1b3c3cfa0c88f54a7a82
f87dfdfea0