Allow for resolving discussions on Wiki pages

What does this MR do and why?

This MR adds the ability to resolve discussions on wiki pages.

References

Resolves #508810 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Open a wiki page on any project
2. create a comment with replies
3. create another reply and click "Resolve thread". The thread should be resolved and collapsed.
4. create another reply on the same thread and click "unresolved thread". The thread should be unresolved.
5. click the "resolve" button in the header of the first comment and verify it also resolves & collapses the thread.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #508810 (closed)