Poll history - setup labs setting (#10039)

* add settings while under development

* very basic tests for roomsummarycard

* empty poll history dialog and option in room summary

* pollS history in settings

* use more user-centric selectors in roomsummarycard test

res/css/views/right_panel/_RoomSummaryCard.pcss

@@ -267,3 +267,7 @@ limitations under the License.
 .mx_RoomSummaryCard_icon_export::before {
     mask-image: url("$(res)/img/element-icons/export.svg");
 }
+
+.mx_RoomSummaryCard_icon_poll::before {
+    mask-image: url("$(res)/img/element-icons/room/composer/poll.svg");
+}