Refactor and improve bulk delete popup

- Improve bulk edit popup with display of avatars and better format
- Refactor both calls of bulk delete to use the same method
- Add display of filename on avatar hover for inline avatars (@Cohee you forgot this one (: )

public/style.css

@@ -3135,7 +3135,7 @@ body.big-avatars .missing-avatar {
     }
 }
 
-span.warning {
+.warning {
     color: var(--warning);
     font-weight: bolder;
 }