As we are rolling out the user profile feature, we'd like to expand the [Usage API](https://www.elastic.co/guide/en/elasticsearch/reference/current/usage-api.html) to report usage stats of user profiles such as (1) number of enabled user profiles and (2) number of user profiles that are [activated](https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-activate-user-profile.html) over the past X days. 

Response of the Usage API already contains a `security` field that groups relevant stats from security related features. We expect the new stats for user profiles should be added under it as well, for example:
```
{
  "security: {
    "user_profile": {
      "activated": 78,
      "recently_activated": 42  <1>
    }
  }
}
```
<1> The use of `recently_` is chosen to avoid the field to be tied to a specific time period so it is easier to evolve the definition in future.

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/Security.java
import org.elasticsearch.ingest.Processor;
import org.elasticsearch.license.License;
import org.elasticsearch.license.LicenseService;
import org.elasticsearch.license.LicensedFeature;
import org.elasticsearch.license.XPackLicenseState;
import org.elasticsearch.plugins.ClusterPlugin;
import org.elasticsearch.plugins.DiscoveryPlugin;
import org.elasticsearch.plugins.ExtensiblePlugin;
import org.elasticsearch.plugins.IngestPlugin;
import org.elasticsearch.plugins.MapperPlugin;
import org.elasticsearch.plugins.NetworkPlugin;
import org.elasticsearch.plugins.Plugin;
import org.elasticsearch.plugins.SearchPlugin;
import org.elasticsearch.plugins.SystemIndexPlugin;
import org.elasticsearch.plugins.interceptor.RestInterceptorActionPlugin;
import org.elasticsearch.repositories.RepositoriesService;
import org.elasticsearch.rest.RestController;
import org.elasticsearch.rest.RestHandler;
import org.elasticsearch.rest.RestHeaderDefinition;
import org.elasticsearch.script.ScriptService;
import org.elasticsearch.search.internal.ShardSearchRequest;
import org.elasticsearch.threadpool.ExecutorBuilder;
import org.elasticsearch.threadpool.FixedExecutorBuilder;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.tracing.Tracer;
import org.elasticsearch.transport.Transport;
import org.elasticsearch.transport.TransportInterceptor;
import org.elasticsearch.transport.TransportRequest;
import org.elasticsearch.transport.TransportRequestHandler;
import org.elasticsearch.transport.netty4.SharedGroupFactory;