Review the relationship between TorSettings and the TorProvider

Currently, in TorSettings we only listen to TorProviderTopics.ProcessIsReady once, and then remove the observer.

Maybe keeping the observer isn't a bad idea after all.

It could help with the restart tor case.

I think currently we're on the safe side just because we save the torrc, but there are open discussions about that.

Also, in the future we could just have the provider to fetch settings (I'd like to move the transformation from the settings object to SETCONF in the provider - of course not in this MR, I just wanted to let you know 🙂).

...

I think it'd make sense to always register and never stop listening to it, since the daemon can be restarted.

However, we should the handler notify a TorSettingsTopic.Ready.

/cc @pierov