Alerting: improve provisioning docs (#50347) (#50618)

* Alerting: improve provisioning docs

* add new provisioning page

* add api docs

* fix formatting and add better descriptions

* fix typo

(cherry picked from commit 862f51216b)

Co-authored-by: Jean-Philippe Quéméner <JohnnyQQQQ@users.noreply.github.com>

docs/sources/developers/http_api/_index.md

@@ -22,8 +22,7 @@ dashboards, creating users, and updating data sources.
 ## HTTP APIs
 
 - [Admin API]({{< relref "admin/" >}})
-- [Alerting Notification Channels API]({{< relref "alerting_notification_channels/" >}})
-- [Alerting API]({{< relref "alerting/" >}})
+- [Alerting Provisioning API]({{< relref "alerting_provisioning/" >}})
 - [Annotations API]({{< relref "annotations/" >}})
 - [Authentication API]({{< relref "auth/" >}})
 - [Dashboard API]({{< relref "dashboard/" >}})
@@ -43,6 +42,11 @@ dashboards, creating users, and updating data sources.
 - [Team API]({{< relref "team/" >}})
 - [User API]({{< relref "user/" >}})
 
+## Deprecated HTTP APIs
+
+- [Alerting Notification Channels API]({{< relref "alerting_notification_channels/" >}})
+- [Alerting API]({{< relref "alerting/" >}})
+
 ## Grafana Enterprise HTTP APIs
 
 Grafana Enterprise includes all of the Grafana OSS APIs as well as those that follow: