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/test/java/org/elasticsearch/xpack/security/profile/ProfileServiceTests.java
profileDocument.applicationData()
                ),
                profileDocument
            ),
            is(false)
        );
        // 
        final ProfileDocumentUser user4 = switch (randomIntBetween(0, 4)) {
            case 0 -> new ProfileDocumentUser(
                randomValueOtherThan(user.username(), () -> randomAlphaOfLengthBetween(5, 8)),
                user.roles(),
                user.realm(),
                user.email(),
                user.fullName()
            );
            case 1 -> new ProfileDocumentUser(
                user.username(),
                randomValueOtherThan(user.roles(), () -> randomList(3, () -> randomAlphaOfLengthBetween(5, 8))),
                user.realm(),
                user.email(),
                user.fullName()
            );
            case 2 -> new ProfileDocumentUser(
                user.username(),
                user.roles(),
                randomValueOtherThan(user.realm(), AuthenticationTestHelper::randomRealmRef),
                user.email(),
                user.fullName()
            );
            case 3 -> new ProfileDocumentUser(