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
randomAlphaOfLength(20),
                randomAlphaOfLengthBetween(3, 18),
                randomList(0, 3, () -> randomAlphaOfLengthBetween(3, 8)),
                Instant.now().toEpochMilli() + randomLongBetween(-100_000, 100_000)
            )
        );
        mockMultiGetRequest(sampleDocumentParameters);
        final PlainActionFuture<ResultsAndErrors<Profile>> future = new PlainActionFuture<>();
        final Set<String> dataKeys = randomFrom(Set.of("app1"), Set.of("app2"), Set.of("app1", "app2"), Set.of());
        profileService.getProfiles(sampleDocumentParameters.stream().map(SampleDocumentParameter::uid).toList(), dataKeys, future);
        final ResultsAndErrors<Profile> resultsAndErrors = future.actionGet();
        assertThat(resultsAndErrors.results().size(), equalTo(sampleDocumentParameters.size()));
        assertThat(resultsAndErrors.errors(), anEmptyMap());
        int i = 0;
        for (Profile profile : resultsAndErrors.results()) {
            final Map<String, Object> applicationData = new HashMap<>();
            if (dataKeys != null && dataKeys.contains("app1")) {
                applicationData.put("app1", Map.of("name", "app1"));
            }
            if (dataKeys != null && dataKeys.contains("app2")) {
                applicationData.put("app2", Map.of("name", "app2"));
            }
            final SampleDocumentParameter sampleDocumentParameter = sampleDocumentParameters.get(i);
            assertThat(
                profile,
                equalTo(
                    new Profile(
                        sampleDocumentParameter.uid,
                        true,
                        sampleDocumentParameter.lastSynchronized,