Enable defining Reconciler in plugin (#3789)

#### What type of PR is this?

/kind feature
/area core
/area plugin

#### What this PR does / why we need it:

This PR adds reconciliation mechanism for plugin. After that, we could define a `Reconciler<Request>` like the following when developing plugin:

```java
@Slf4j
@Component
public class ApplicationReconciler implements Reconciler<Reconciler.Request> {

    @Override
    public Result reconcile(Request request) {
        log.info("Application {} changed.", request);
        return Result.doNotRetry();
    }

    @Override
    public Controller setupWith(ControllerBuilder builder) {
        return builder
            .extension(new Application())
            .workerCount(1)
            .build();
    }
}
```

You can reconcile any extensions as needed.

Meanwhile, all plugins will be stopped when Halo is shutting down.

#### Which issue(s) this PR fixes:

Fixes https://github.com/halo-dev/halo/issues/3783

#### Does this PR introduce a user-facing change?

```release-note
支持在插件中定义 Reconciler
```

application/src/main/java/run/halo/app/plugin/HaloPluginManager.java

@@ -21,6 +21,7 @@ import org.pf4j.PluginState;
 import org.pf4j.PluginStateEvent;
 import org.pf4j.PluginWrapper;
 import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -41,7 +42,7 @@ import run.halo.app.plugin.event.HaloPluginStoppedEvent;
  */
 @Slf4j
 public class HaloPluginManager extends DefaultPluginManager
-    implements ApplicationContextAware, InitializingBean {
+    implements ApplicationContextAware, InitializingBean, DisposableBean {
 
     private final Map<String, PluginStartingError> startingErrors = new HashMap<>();
 
@@ -403,5 +404,10 @@ public class HaloPluginManager extends DefaultPluginManager
             springComponentsFinder.removeComponentsStorage(pluginId);
         }
     }
+
+    @Override
+    public void destroy() throws Exception {
+        stopPlugins();
+    }
     // end-region
 }

application/src/main/java/run/halo/app/plugin/PluginControllerManager.java

@@ -0,0 +1,58 @@
+package run.halo.app.plugin;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Stream;
+import org.springframework.context.event.EventListener;
+import org.springframework.core.ResolvableType;
+import org.springframework.stereotype.Component;
+import run.halo.app.extension.ExtensionClient;
+import run.halo.app.extension.controller.ControllerManager;
+import run.halo.app.extension.controller.DefaultControllerManager;
+import run.halo.app.extension.controller.Reconciler;
+import run.halo.app.extension.controller.Reconciler.Request;
+import run.halo.app.plugin.event.HaloPluginBeforeStopEvent;
+import run.halo.app.plugin.event.HaloPluginStartedEvent;
+
+@Component
+public class PluginControllerManager {
+
+    private final Map<String, ControllerManager> controllerManagerMap;
+
+    private final ExtensionClient client;
+
+    public PluginControllerManager(ExtensionClient client) {
+        this.client = client;
+        controllerManagerMap = new ConcurrentHashMap<>();
+    }
+
+    @EventListener
+    public void onPluginStarted(HaloPluginStartedEvent event) {
+        var plugin = event.getPlugin();
+
+        var controllerManager = controllerManagerMap.computeIfAbsent(plugin.getPluginId(),
+            id -> new DefaultControllerManager(client));
+
+        getReconcilers(plugin.getPluginId())
+            .forEach(controllerManager::start);
+    }
+
+    @EventListener
+    public void onPluginBeforeStop(HaloPluginBeforeStopEvent event) {
+        // remove controller manager
+        var plugin = event.getPlugin();
+        var controllerManager = controllerManagerMap.remove(plugin.getPluginId());
+        if (controllerManager != null) {
+            // stop all reconcilers
+            getReconcilers(plugin.getPluginId())
+                .forEach(controllerManager::stop);
+        }
+    }
+
+    private Stream<Reconciler<Request>> getReconcilers(String pluginId) {
+        var context = ExtensionContextRegistry.getInstance().getByPluginId(pluginId);
+        return context.<Reconciler<Request>>getBeanProvider(
+                ResolvableType.forClassWithGenerics(Reconciler.class, Request.class))
+            .orderedStream();
+    }
+}