bug#52417: Mark ring navigation could be two-way

[Juri Linkov]

>> Emacs could have this too by providing a command which allows
>> moving forward in the mark ring.
>
> FWIW, we've recently added xref-go-forward, bound to 'C-M-,', which pairs
> with xref-go-back (which was renamed at the same time), bound to 'M-,'.
>
> A fair number of commands both push to mark ring and call
> xref-push-marker-stack, so you might find this useful.

Another idea: add a command that will display a *xref* buffer
with lines of locations extracted from the global-mark-ring.
This will allow visiting mark locations from the mark list.
Maybe this can be implemented by just adding a new xref backend?