Apparently some PDF files can have annotations with `URI` entries ending with `null` characters, thus breaking the links.
To handle this edge-case of bad PDFs, this patch moves the already existing utility function from `ui_utils.js` into `util.js`, in order to fix those URLs.
Fixes 6832.
*This regressed in PR 5356.*
Rather than just backing out the offending code, this patch restores scrolling in PresentationMode by making the `overflow: hidden;` check optional and letting the callers that need it (e.g. `PDFFindController`) opt-in to use it.
Since some browsers render `null` characters, and others don't, this patch adds a way to remove them to prevent display issues in the viewer UI.
Given that documents may contain very long outlines, I've added a utility function to avoid creating a lot of unnecessary `RegExp` objects.
To avoid any future issues, this utility function is used for both the outline and the attachments.
Fixes 6416.