Example stable plugins with settings (#92334)

New stable plugins example with injected settings.
Plugin developer creates an interface and annotates it with @AnalysisSettings.
The constructor in a plugin component (annotated with @NamedComponent) has to be annotated with @Inject
Upon plugin component creation an implementation of the interface will be created - a dynamic proxy - which will delegate methods from interface to properties in a Settings instance.
This PR introduces an example of using all currently supported types : int, long, double, string and list (of strings)
relates ##88980

libs/plugin-api/src/main/java/org/elasticsearch/plugin/api/settings/ListSetting.java

@@ -23,4 +23,6 @@ public @interface ListSetting {
      * A name of a setting
      */
     String path();
+
+    String[] def() default {};
 }