Wait for verification request on login

Basically just changes to the designed screen to wait for an incoming
verification request in order to verify the device & cross-sign it.

Fixes https://github.com/vector-im/riot-web/issues/11215
Fixes https://github.com/vector-im/riot-web/issues/11217

res/css/structures/auth/_CompleteSecurity.scss

@@ -37,6 +37,10 @@ limitations under the License.
     font-size: 15px;
 }
 
+.mx_CompleteSecurity_waiting {
+    color: $notice-secondary-color;
+}
+
 .mx_CompleteSecurity_actionRow {
     display: flex;
     justify-content: flex-end;