Show that issue search result matched on a note

Problem to solve

Related to #15645 (comment 2141977597)

Advanced search issues search will also search comments (notes) on issues. Highlighting in the search results shows users where the match occurred. If an issue result only matches on a comment, it will be confusing to the user.

Proposal

Add a visual identifier on an issue result if the match was only on a comment on an issue and not the issue title or description.

We could do something similar to file only matches in code search