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.xpack.security.audit.AuditTrail;
import org.elasticsearch.xpack.security.audit.AuditTrailService;
import org.elasticsearch.xpack.security.audit.logfile.LoggingAuditTrail;
import org.elasticsearch.xpack.security.authc.ApiKeyService;
import org.elasticsearch.xpack.security.authc.AuthenticationService;
import org.elasticsearch.xpack.security.authc.InternalRealms;
import org.elasticsearch.xpack.security.authc.Realms;
import org.elasticsearch.xpack.security.authc.TokenService;
import org.elasticsearch.xpack.security.authc.esnative.NativeUsersStore;
import org.elasticsearch.xpack.security.authc.esnative.ReservedRealm;
import org.elasticsearch.xpack.security.authc.jwt.JwtRealm;
import org.elasticsearch.xpack.security.authc.service.CachingServiceAccountTokenStore;
import org.elasticsearch.xpack.security.authc.service.FileServiceAccountTokenStore;
import org.elasticsearch.xpack.security.authc.service.IndexServiceAccountTokenStore;
import org.elasticsearch.xpack.security.authc.service.ServiceAccountService;
import org.elasticsearch.xpack.security.authc.support.SecondaryAuthenticator;
import org.elasticsearch.xpack.security.authc.support.mapper.NativeRoleMappingStore;
import org.elasticsearch.xpack.security.authz.AuthorizationService;
import org.elasticsearch.xpack.security.authz.DlsFlsRequestCacheDifferentiator;
import org.elasticsearch.xpack.security.authz.SecuritySearchOperationListener;
import org.elasticsearch.xpack.security.authz.accesscontrol.OptOutQueryCache;
import org.elasticsearch.xpack.security.authz.interceptor.BulkShardRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.DlsFlsLicenseRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.IndicesAliasesRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.RequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.ResizeRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.SearchRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.ShardSearchRequestInterceptor;
import org.elasticsearch.xpack.security.authz.interceptor.UpdateRequestInterceptor;
import org.elasticsearch.xpack.security.authz.store.CompositeRolesStore;