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
when(client.prepareSearch(SECURITY_PROFILE_ALIAS)).thenReturn(
            new SearchRequestBuilder(client, SearchAction.INSTANCE).setIndices(SECURITY_PROFILE_ALIAS)
        );
        this.profileIndex = SecurityMocks.mockSecurityIndexManager(SECURITY_PROFILE_ALIAS);
        final ClusterService clusterService = mock(ClusterService.class);
        final ClusterState clusterState = mock(ClusterState.class);
        when(clusterService.state()).thenReturn(clusterState);
        final DiscoveryNodes discoveryNodes = mock(DiscoveryNodes.class);
        when(clusterState.nodes()).thenReturn(discoveryNodes);
        minNodeVersion = VersionUtils.randomVersionBetween(random(), Version.V_7_17_0, Version.CURRENT);
        when(discoveryNodes.getMinNodeVersion()).thenReturn(minNodeVersion);
        this.profileService = new ProfileService(
            Settings.EMPTY,
            Clock.systemUTC(),
            client,
            profileIndex,
            clusterService,
            name -> new DomainConfig(name, Set.of(), false, null),
            threadPool
        );
    }
    @After
    public void stopThreadPool() {
        terminate(threadPool);
    }
    public void testGetProfilesByUids() {
        final List<SampleDocumentParameter> sampleDocumentParameters = randomList(
            1,
            5,
            () -> new SampleDocumentParameter(