It turns out that one "Connection" per RunControl doesn't map
well to the uses we have. Instead, RunWorkers need to know
individually how to connect to the place where they can work,
but they are already specific enough to be able to use a
standard class (like QUrl) as their way to specify the needed
entry point.

In theory one could see a RunControl's connection as an
aggregation of its workers connection bits, but that does
not really seem to be needed in code.

As consequence, replace UrlConnection by a plain QUrl, and also
the HostName connection by a QUrl with hostName set.

Change-Id: I40c97e37779314ac0a77041e864a18eadb78f987
Reviewed-by: Vikas Pachdha <vikas.pachdha@qt.io>