Fix intra doc links not generated inside footnote definitions Fixes #132208. The problem was that we were running the `Footnote` "pass" before the `LinkReplacer` one. Sadly, the change is bigger than it should because we can't specialize the `Iterator` trait implementation, forcing me to add a new type to handle the other `Iterator` kind (the one which still has the `Range`). r? ``@notriddle``