DocManager: Also listen to documentUrlChanged signal
Currently we only listen to ReadOnlyPart::urlChanged signal. This can lead to issues where we might end up with multiple documents with the same url open in a single viewspace.
One of the case I found is:
- open Kate with a project e.g.,
kate -b -n /path/to/repo
- open a file in the project
- use the urlbar to open another file in a different project
=> You get the same file open twice.
The reason is that the part signal fires later and someone (view manager) requests a document for the new url before that and we end up with 2 views for the same document.