Font Awesome 6 Issues

[TimWolla]

• [x] #4991
• [x] “Unsafe HTML” button in editor is missing the icon:
• [x] Comment Buttons look off (with one of them miscolored):
• [ ] Icon coloring in systemCheck.tpl no longer applied. This makes it impossible to differentiate between "warning" and "hard error".
• [x] Make the “active” bell solid in NotificationSettings. This makes the visual difference between “disabled” and “enabled” clearer, especially since the colored outline is fairly thin. Mockup (middle is the suggested version):
• [ ] Incorrect icon color for style edit buttons in StyleListPage.