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/SecurityUsageTransportAction.java
private final Settings settings;
    private final XPackLicenseState licenseState;
    private final Realms realms;
    private final CompositeRolesStore rolesStore;
    private final NativeRoleMappingStore roleMappingStore;
    private final IPFilter ipFilter;
    @Inject
    public SecurityUsageTransportAction(
        TransportService transportService,
        ClusterService clusterService,
        ThreadPool threadPool,
        ActionFilters actionFilters,
        IndexNameExpressionResolver indexNameExpressionResolver,
        Settings settings,
        XPackLicenseState licenseState,
        SecurityUsageServices securityServices
    ) {
        super(
            XPackUsageFeatureAction.SECURITY.name(),
            transportService,
            clusterService,
            threadPool,
            actionFilters,
            indexNameExpressionResolver
        );
        this.settings = settings;
        this.licenseState = licenseState;