Refine the colors of some more components (#12343)

* Refine the colors of some more components

This is a reintroduction of https://github.com/matrix-org/matrix-react-sdk/pull/12255, and should be the last part of the Compound color refinement work (https://github.com/element-hq/element-web/issues/26992). I've updated the following components to reflect design decisions (https://www.figma.com/file/pqhlirZFEwEp5XpudSbiia/Theming-Web-templates?type=design&node-id=80-60219&mode=design&t=mjqwylUie1vRwzOV-0) that will help them fit in better with the new design system:

- Message bubbles
- Pills
- Sent indicators
- Jump to bottom/unread buttons
- Composer placeholder
- Notification badges
- Room sublists
- Verification shields
- Date separators
- Tooltips

Closes https://github.com/element-hq/element-web/issues/22122

* Update some screenshots

res/css/views/rooms/_RoomSublist.pcss

@@ -118,7 +118,7 @@ limitations under the License.
                 mask-position: center;
                 mask-size: contain;
                 mask-repeat: no-repeat;
-                background: $muted-fg-color;
+                background: var(--cpd-color-icon-secondary);
             }
         }
 
@@ -167,7 +167,7 @@ limitations under the License.
                     mask-position: center;
                     mask-size: contain;
                     mask-repeat: no-repeat;
-                    background-color: $tertiary-content;
+                    background-color: var(--cpd-color-icon-secondary);
                     mask-image: url("$(res)/img/feather-customised/chevron-down.svg");
                 }