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/qa/profile/src/javaRestTest/java/org/elasticsearch/xpack/security/profile/ProfileIT.java
try {
            
            client.setNodes(List.of(node0));
            final Map<String, Object> responseMap0 = responseAsMap(client.performRequest(activateProfileRequest));
            final Instant start = Instant.now();
            
            final Map<String, Object> responseMap1 = responseAsMap(client.performRequest(activateProfileRequest));
            assumeTrue("Test is running too slow", start.plus(30, ChronoUnit.SECONDS).isAfter(Instant.now()));
            assertThat(responseMap1.get("_doc"), equalTo(responseMap0.get("_doc")));
            
            client.setNodes(List.of(node1));
            final Map<String, Object> responseMap2 = responseAsMap(client.performRequest(activateProfileRequest));
            assumeTrue("Test is running too slow", start.plus(30, ChronoUnit.SECONDS).isAfter(Instant.now()));
            assertThat(responseMap2.get("_doc"), not(equalTo(responseMap0.get("_doc"))));
            
            final Map<String, Object> responseMap3 = responseAsMap(client.performRequest(activateProfileRequest));
            assertTrue("Test is running too slow", Instant.now().toEpochMilli() - (long) responseMap2.get("last_synchronized") < 30_000L);
            assertThat(responseMap3.get("_doc"), equalTo(responseMap2.get("_doc")));
        } finally {
            client.setNodes(originalNodes);
        }
    }
    public void testGetUsersWithProfileUid() throws IOException {
        final String username = randomAlphaOfLengthBetween(3, 8);
        final Request putUserRequest = new Request("PUT", "_security/user/" + username);
        putUserRequest.setJsonEntity("{\"password\":\"x-pack-test-password\",\"roles\":[\"superuser\"]}");
        assertOK(adminClient().performRequest(putUserRequest));
        final Map<String, Object> profile = doActivateProfile(username, "x-pack-test-password");
        final Request getUserRequest = new Request("GET", "_security/user" + (randomBoolean() ? "/" + username : ""));
        getUserRequest.addParameter("with_profile_uid", "true");