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
}
    public void testActivateWhenShouldSkipUpdateForActivateReturnsFalseFirst() throws IOException {
        final ProfileService service = spy(profileService);
        doAnswer(
            invocation -> new UpdateRequestBuilder(
                client,
                UpdateAction.INSTANCE,
                SECURITY_PROFILE_ALIAS,
                (String) invocation.getArguments()[1]
            )
        ).when(client).prepareUpdate(eq(SECURITY_PROFILE_ALIAS), anyString());
        // 
        final Exception updateException;
        final VersionConflictEngineException versionConflictException = new VersionConflictEngineException(mock(ShardId.class), "", "");
        if (randomBoolean()) {
            updateException = new RemoteTransportException("", versionConflictException);
        } else {
            updateException = versionConflictException;
        }
        doAnswer(invocation -> {
            @SuppressWarnings("unchecked")
            final ActionListener<UpdateResponse> listener = (ActionListener<UpdateResponse>) invocation.getArguments()[1];
            listener.onFailure(updateException);
            return null;
        }).when(service).doUpdate(any(), anyActionListener());
        final Subject subject = AuthenticationTestHelper.builder().realm().build().getEffectiveSubject();
        final var versionedDocument = new ProfileService.VersionedDocument(ProfileDocument.fromSubject(subject), 1, 0);
        final XContentBuilder builder = XContentFactory.jsonBuilder();
        builder.startObject().field("user_profile", versionedDocument.doc()).endObject();
        SecurityMocks.mockGetRequest(