To be able to label incoming tor connections as different from normal localhost connections in e.g. `getpeerinfo` and the peers list in the GUI it'd be useful to have them connect on an alternative local-only port. Or even better, a UNIX socket.

For manually set-up hidden services this would have to be configured manually and could add a `hsport` option or such. The external port would still appear as `XXXXXXXXX.onion:8333`, however internally it would redirect to a that port.

In the case of `torcontrol` this would be easy to set up automatically. It could add a new (localhost) binding port automatically and this code would have to be changed:
- https://github.com/bitcoin/bitcoin/blob/master/src/torcontrol.cpp#L441
- https://github.com/bitcoin/bitcoin/blob/master/src/torcontrol.cpp#L477

{
    FILE *f = fsbridge::fopen(filename, "wb");
    if (f == nullptr)
        return false;
    if (fwrite(data.data(), 1, data.size(), f) != data.size()) {
        fclose(f);
        return false;
    }
    fclose(f);
    return true;
}
/** Controller that connects to Tor control socket, authenticate, then create
 * and maintain an ephemeral onion service.
 */
class TorController
{
public:
    TorController(struct event_base* base, const std::string& target);
    ~TorController();
    
    fs::path GetPrivateKeyFile();
    
    void Reconnect();