Fixed a trailing whitespace

Implement an Android-specific transport, that relies on the Java side
to start the domain fronting proxy.

GeckoView is missing some API we use on desktop for the integration
with the tor daemon, such as subprocess.
Therefore, we need to implement them in Java and plumb the data
back and forth between JS and Java.

Use a custom TorProcessAndroid in the TorProvider on Android.

Test to plumb down the circuit display data

Switch from a gate based on the update channel to a gate based on a
pref.
Also, draft the JS part for TorSettings events.

Keep only a TorProcess in memory at a time.
When we forget a process from JS, we also delete the Java instance.
When we start a new process, we delete the old one if any (but emit a
warning in logs, in case).

Make TorProcessAndroid.forget signal to Java the forget request.