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
getLicenseState().addListener(allRolesStore::invalidateAll);
        final AuthenticationFailureHandler failureHandler = createAuthenticationFailureHandler(realms, extensionComponents);
        final OperatorPrivilegesService operatorPrivilegesService;
        final boolean operatorPrivilegesEnabled = OPERATOR_PRIVILEGES_ENABLED.get(settings);
        if (operatorPrivilegesEnabled) {
            logger.info("operator privileges are enabled");
            operatorPrivilegesService = new OperatorPrivileges.DefaultOperatorPrivilegesService(
                getLicenseState(),
                new FileOperatorUsersStore(environment, resourceWatcherService),
                new OperatorOnlyRegistry(clusterService.getClusterSettings())
            );
        } else {
            operatorPrivilegesService = OperatorPrivileges.NOOP_OPERATOR_PRIVILEGES_SERVICE;
        }
        authcService.set(
            new AuthenticationService(
                settings,
                realms,
                auditTrailService,
                failureHandler,
                threadPool,
                anonymousUser,
                tokenService,
                apiKeyService,
                serviceAccountService,
                operatorPrivilegesService
            )
        );