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
components.add(authcService.get());
        systemIndices.getMainIndexManager().addStateListener(authcService.get()::onSecurityIndexStateChange);
        Set<RequestInterceptor> requestInterceptors = Sets.newHashSet(
            new ResizeRequestInterceptor(threadPool, getLicenseState(), auditTrailService),
            new IndicesAliasesRequestInterceptor(threadPool.getThreadContext(), getLicenseState(), auditTrailService)
        );
        if (XPackSettings.DLS_FLS_ENABLED.get(settings)) {
            requestInterceptors.addAll(
                Arrays.asList(
                    new SearchRequestInterceptor(threadPool, getLicenseState(), clusterService),
                    new ShardSearchRequestInterceptor(threadPool, getLicenseState(), clusterService),
                    new UpdateRequestInterceptor(threadPool, getLicenseState()),
                    new BulkShardRequestInterceptor(threadPool, getLicenseState()),
                    new DlsFlsLicenseRequestInterceptor(threadPool.getThreadContext(), getLicenseState())
                )
            );
        }
        requestInterceptors = Collections.unmodifiableSet(requestInterceptors);
        final AuthorizationService authzService = new AuthorizationService(
            settings,
            allRolesStore,
            clusterService,
            auditTrailService,
            failureHandler,
            threadPool,
            anonymousUser,
            getAuthorizationEngine(),
            requestInterceptors,
            getLicenseState(),
            expressionResolver,