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/SecurityInfoTransportActionTests.java
realmsUsageStats.put("type" + i, realmUsage);
            realmUsage.put("key1", Arrays.asList("value" + i));
            realmUsage.put("key2", Arrays.asList(i));
            realmUsage.put("key3", Arrays.asList(i % 2 == 0));
        }
        configureRealmsUsage(realmsUsageStats);
        final boolean anonymousEnabled = randomBoolean();
        if (anonymousEnabled) {
            settings.put(AnonymousUser.ROLES_SETTING.getKey(), "foo");
        }
        final boolean fips140Enabled = randomBoolean();
        if (fips140Enabled) {
            settings.put("xpack.security.fips_mode.enabled", true);
        }
        final boolean operatorPrivilegesEnabled = randomBoolean();
        if (operatorPrivilegesEnabled) {
            settings.put("xpack.security.operator_privileges.enabled", true);
        }
        var usageAction = newUsageAction(settings.build());
        PlainActionFuture<XPackUsageFeatureResponse> future = new PlainActionFuture<>();
        usageAction.masterOperation(null, null, null, future);
        SecurityFeatureSetUsage securityUsage = (SecurityFeatureSetUsage) future.get().getUsage();
        BytesStreamOutput out = new BytesStreamOutput();
        securityUsage.writeTo(out);
        XPackFeatureSet.Usage serializedUsage = new SecurityFeatureSetUsage(out.bytes().streamInput());
        for (XPackFeatureSet.Usage usage : Arrays.asList(securityUsage, serializedUsage)) {
            assertThat(usage, is(notNullValue()));
            assertThat(usage.name(), is(XPackField.SECURITY));
            assertThat(usage.enabled(), is(enabled));
            assertThat(usage.available(), is(true));