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/profile/ProfileService.java
.filter(ProfileDocument::enabled)
                        .map(doc -> Map.entry(doc.uid(), doc.user().toSubject()))
                        .toList(),
                    resultsAndErrors.errors()
                );
            } else {
                return new ResultsAndErrors<>(List.of(), Map.of());
            }
        }));
    }
    
    /**
     * Create a new profile or update an existing profile for the user of the given Authentication.
     * @param authentication This is the object from which the profile will be created or updated.
     *                       It contains information about the username and relevant realms and domain.
     *                       Note that this authentication object does not belong to the authenticating user
     *                       because the associated ActivateProfileRequest provides the authentication information
     *                       in the request body while the authenticating user is the one that has privileges
     *                       to submit the request.
     */
    public void activateProfile(Authentication authentication, ActionListener<Profile> listener) {
        final Subject subject = authentication.getEffectiveSubject();
        if (Subject.Type.USER != subject.getType()) {
            listener.onFailure(
                new IllegalArgumentException(
                    "profile is supported for user only, but subject is a [" + subject.getType().name().toLowerCase(Locale.ROOT) + "]"
                )
            );
            return;
        }