Improve iteration reference filter to parse URL
An iteration URL, unlike issue/epic/milestone URL, isn't parsed and turned into a reference.
As an example, the milestone U*RLhttps://gitlab.com/gitlab-org/gitlab/-/milestones/30
is turned into a reference by the milestone reference filter:
Iterations urls like https://gitlab.com/gitlab-org/gitlab/-/cadences/16671/iterations/66226 do not get processed by the iteration reference filter.
The iteration reference filter should be updated to parse urls to make the user experience more consistent across different domain objects.
The issue was initially raised in !96528 (comment 1083775507).