Support binding to port 0

[BlinkyStitt]

If you ask linux to bind to port 0, it will automatically pick an open port for you. This can be really helpful when running multiple instances of ganache on the same machine. Currently, ganache says Invalid port number '0'

Please make ganache support binding to port 0.

It would also be helpful (though not necessary) if it wrote this port to a file somewhere.

[davidmurdoch]

uWebSockets, the library we use, does support this. We just need to provide a way for the user to get this port - we should probably just copy node's API here.

We'll also need to update our fork of uwebsockets as I don't think the fallback exposes the feature.

Additional context may be found in this PR comment.

Would you like to work this issue?

[BlinkyStitt]

You probably don't want me writing any JavaScript haha

[davidmurdoch]

Haha. No worries. Do you know of any cli tools that can "bind" to port 0 and then output the actual port to a file?