Support "r" and "up" shortcuts in work item comments

Comments regression: If you select text in a comment in a legacy issuable or an MR then hit r, the selected text is inserted into a new reply in that comment's thread as a blockquote. If you do the same thing when you have selected text in the description, then it will insert the blockquote into a new top-level comment.

In a work item, it always creates a new top-level comment. Something is broken there.

In a legacy issuable or an MR, if you focus the new reply input on a thread then press up, it will put your most recent comment in that thread in the edit state and allow you to edit it. This does not work on work items.

via https://gitlab.com/gitlab-org/gitlab/-/issues/512715#note_2366873007