Add support for rendering comments in content editor

What does this MR do and why?

Add support for inserting and showing HTML comments in rich text editor.

Screenshots or screen recordings

How to set up and validate locally

1. Open a wiki page.
2. In the + dropdown menu, select, Comment.
3. An HTML comment should insert.
4. Save. The comment should not be visible on the page, but still be visible when editing the source, or rich text.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #342173 (closed)