Alerting: unable to configure webhook notification timeout

### What happened? We have a contact point configured with a webhook that tries to send the alerts to an external service that processes them. Alerts triggered by the internal Grafana manager as multidimensional alert rules. We usually have situations where the number of alerts are quite high and the process of the alerts can elapse more than 30s. The following issue #58687 describes the same case, but it was closed as it derived into screenshot processes, not resolving the original issue. So: - Is there a way to increase the notification timeout? - Is there a reason why the timeout is hardcoded to 30s? ### What did you expect to happen? The notification answers OK with custom timeout on contact points configuration ### Did this work before? No ### How do we reproduce it? 1. Up a simple http listener that answers after 30s 2. Create an alert rule that fires an alert 3. Configure contact point to use the http listener 4. Create a notifiaction rule that matches the rules 5. Wait until the alert is fired and check the health of the contact point/notification policy ### Is the bug inside a dashboard panel? _No response_ ### Environment (with versions)? Grafana: 10.0.3 ### Grafana platform? Docker ### Datasource(s)? _No response_