Notify users to restart Elasticsearch after plugin installation (#66723)

* Add message to elasticsearch-plugin CLI output to notify users to restart
Elasticsearch after plugin installation

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

distribution/tools/plugin-cli/src/main/java/org/elasticsearch/plugins/InstallPluginCommand.java

@@ -265,6 +265,7 @@ class InstallPluginCommand extends EnvironmentAwareCommand {
                 throw installProblem;
             }
         }
+        terminal.println("-> Please restart Elasticsearch to activate any plugins installed");
     }
 
     Build.Flavor buildFlavor() {