There is an issue where chat message processing breaks due to
unhandles `SocketError` exceptions originating in the SSRF check,
specifically in `FinalDestination::Resolver`.
This change gives `FinalDestination::SSRFDetector` a new error class
to wrap the `SocketError` in, and haves the `RetrieveTitle` class
handle that error gracefully.
We were adding to the resolver's work queue before setting up the `@lookup` and `@parent` information. That could lead to the lookup being performed on the wrong (or `nil`) hostname. This also lead to some flakiness in specs.
