Remove the always-on alarm-to-event conversion (EventHookCallback) (#13925)

A triggered alarm is no longer synthesized into the events pipeline as an
Alarm/AlarmRecovery event; events now originate only from real event sources
(agents, SkyWalking CLI, Kubernetes Event Exporter). Alarms remain available
through the alarm store (getAlarm/queryAlarms) and the configured alarm hooks.

- Delete EventHookCallback and its unconditional registration in NotifyHandler.
- Delete EventHookCallbackTest.
- Drop the now-dead event-analyzer dependency from server-alarm-plugin.
- Remove the 'Alarm' Known-Event row from event.md; update the e2e guide recipe.
- Update the alarm/baseline e2e expected files to assert 'events: []' — the
  alarm now correlates no synthetic event (swctl 'alarm ls' still projects the
  events field, so the expectation must assert the empty list).
- Add a CHANGES entry.

Author: wu-sheng

docs/en/changes/changes.md

@@ -2,6 +2,7 @@
 
 #### Project
 
+* Remove the always-on alarm-to-event conversion (`EventHookCallback`). A triggered alarm is no longer synthesized into the events pipeline as an `Alarm`/`AlarmRecovery` event; events now originate only from real event sources (agents, SkyWalking CLI, Kubernetes Event Exporter). Alarms remain available through the alarm store (`getAlarm`/`queryAlarms`) and the configured alarm hooks. This drops a documented "Known Event" and removes 1-2 synthetic event records per alarm fire.
 * **New `queryAlarms` GraphQL query — entity / layer / rule filters for alarms.** Adds
   a comprehensive alarm query API alongside the legacy `getAlarm`. The new
   `queryAlarms(condition: AlarmQueryCondition!): Alarms` accepts a single input type

docs/en/concepts-and-designs/event.md

@@ -66,7 +66,6 @@ service / instance / endpoint.
 | :----: | :----: | :-----| :---- |
 | Start | Normal | When your Java Application starts with SkyWalking Agent installed, the `Start` Event will be created. | Reported from SkyWalking agent. |
 | Shutdown | Normal | When your Java Application stops with SkyWalking Agent installed, the `Shutdown` Event will be created. | Reported from SkyWalking agent. |
-| Alarm | Error | When the Alarm is triggered, the corresponding `Alarm` Event will is created. | Reported from internal SkyWalking OAP. |
 
 The following events are all reported
 by [Kubernetes Event Exporter](http://github.com/apache/skywalking-kubernetes-event-exporter), in order to see these

oap-server/server-alarm-plugin/pom.xml

@@ -38,11 +38,6 @@
             <artifactId>library-util</artifactId>
             <version>${project.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.apache.skywalking</groupId>
-            <artifactId>event-analyzer</artifactId>
-            <version>${project.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.skywalking</groupId>
             <artifactId>mqe-rt</artifactId>

oap-server/server-alarm-plugin/src/main/java/org/apache/skywalking/oap/server/core/alarm/provider/EventHookCallback.java

@@ -241,7 +241,6 @@ public void init(AlarmCallback... callbacks) {
         allCallbacks.add(new WechatHookCallback(alarmRulesWatcher));
         allCallbacks.add(new DingtalkHookCallback(alarmRulesWatcher));
         allCallbacks.add(new FeishuHookCallback(alarmRulesWatcher));
-        allCallbacks.add(new EventHookCallback(this.manager));
         allCallbacks.add(new WeLinkHookCallback(alarmRulesWatcher));
         allCallbacks.add(new PagerDutyHookCallback(alarmRulesWatcher));
         allCallbacks.add(new DiscordHookCallback(alarmRulesWatcher));