Add filtering by attention requests

I added the attention-requests docs in !81250 (merged) but had to redact the portion about filters because I wasn't sure how I wanted to do it. This merge request gardens in attention requests to the ways that users can filter merge requests.

Related issues and merge requests

• Related to !81250 (merged) where I added the rest of the docs
• Related to #353235 (closed)
• Related to #356694 (closed)