Automatically expand hidden discussions when accessed via a permalink hash (closes #19304)

What does this MR do?

Addresses "Auto-expand a discussion note when we arrive via anchor" (issue #19304 (closed))

Are there points in the code the reviewer needs to double check?

Let me know if the code is consistent with community standards (not 100% sure about indentation of chained jQuery actions)

I don't think this MR warrants any unit tests or documentation, but let me know if you disagree. I'll add the requisite CHANGELOG entry upon approval.

Why was this MR needed?

Currently, if a discussion is accessed via a permalink to an "outdated" diff discussion, the anchor will not bring you to the expected part of the page.

What are the relevant issue numbers?

#19304 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together