enhance: add permalinks to pull request reviews (#38849)

1. Make review threads linkable via `#pullrequestreview-<reviewID>`
2. Improve CSS so username and timestamp go colored on hover.
3. CSS cleanup, remove dead rules, nonexistant class name, make `.suppressed` actually do what it says in the doc above.

web_src/css/base.css

@@ -301,9 +301,7 @@ a.silenced,
 }
 
 a:hover,
-a.suppressed:hover,
 a.muted:hover,
-a.muted:hover [class*="color-text"],
 .muted-links a:hover {
   color: var(--color-primary);
 }