[Dev] Stop commenting "Closes .." on PR, comment on issue instead

### Describe the enhancement requested

It's maybe two separate issues, but:

- The PR workflow both updates the first comment to add a "Closes .." and adds a comment with the same text. I think just updating the top comment is sufficient (the notification from the extra comment isn't useful, and for the rest both updates have the same content).
- On the other hand, what I personally would find useful is that we add a comment to the issue instead that says something like "A PR was opened that would close this issue: ...".
If you are subscribed to an issue, you can miss that there is a PR for it until that PR gets merged / the issue closed (on JIRA, you got such a notification)

### Component(s)

Developer Tools

Locate the PR workflow responsible for updating the first comment and posting the duplicate "Closes .." comment, then trace how it can notify the linked issue. Done means the redundant PR comment is removed and the issue receives a comment linking the opened PR, with the existing first-comment update preserved.

Written by the indexing model from the issue text.