[MM-57067][MM-57006][MM-57328] Acknowledge websocket POSTED events that may result in a notification on the web client (#26604)

* Acknowledge POSTED events that may result in a notification

* Remove temporary metrics

* Add Desktop App support

* Merge'd

* Add some tests

* PR feedback

* Rework window is focused check

* Oops

* Move mentions/followers ACK to posted ACK broadcast hook

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/components/login/login.tsx

@@ -267,7 +267,7 @@ const Login = ({onCustomizeHeader}: LoginProps) => {
                         closeSessionExpiredNotification.current = undefined;
                     }
                 },
-            }).then((closeNotification) => {
+            }).then(({callback: closeNotification}) => {
                 closeSessionExpiredNotification.current = closeNotification;
             }).catch(() => {
                 // Ignore the failure to display the notification.