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
Automatons.addSettings(settingsList);
        settingsList.addAll(CompositeRolesStore.getSettings());
        settingsList.addAll(DocumentSubsetBitsetCache.getSettings());
        settingsList.add(FieldPermissionsCache.CACHE_SIZE_SETTING);
        settingsList.add(TokenService.TOKEN_EXPIRATION);
        settingsList.add(TokenService.DELETE_INTERVAL);
        settingsList.add(TokenService.DELETE_TIMEOUT);
        settingsList.addAll(SSLConfigurationSettings.getProfileSettings());
        settingsList.add(ApiKeyService.PASSWORD_HASHING_ALGORITHM);
        settingsList.add(ApiKeyService.DELETE_TIMEOUT);
        settingsList.add(ApiKeyService.DELETE_INTERVAL);
        settingsList.add(ApiKeyService.CACHE_HASH_ALGO_SETTING);
        settingsList.add(ApiKeyService.CACHE_MAX_KEYS_SETTING);
        settingsList.add(ApiKeyService.CACHE_TTL_SETTING);
        settingsList.add(ApiKeyService.DOC_CACHE_TTL_SETTING);
        settingsList.add(NativePrivilegeStore.CACHE_MAX_APPLICATIONS_SETTING);
        settingsList.add(NativePrivilegeStore.CACHE_TTL_SETTING);
        settingsList.add(OPERATOR_PRIVILEGES_ENABLED);
        settingsList.add(CachingServiceAccountTokenStore.CACHE_TTL_SETTING);
        settingsList.add(CachingServiceAccountTokenStore.CACHE_HASH_ALGO_SETTING);
        settingsList.add(CachingServiceAccountTokenStore.CACHE_MAX_TOKENS_SETTING);
        settingsList.add(SimpleRole.CACHE_SIZE_SETTING);
        
        settingsList.add(
            Setting.listSetting(
                SecurityField.setting("hide_settings"),
                Collections.emptyList(),
                Function.identity(),
                Property.NodeScope,
                Property.Filtered