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/main/java/org/elasticsearch/xpack/security/Security.java
if (storedHashAlgo.toLowerCase(Locale.ROOT).startsWith("pbkdf2") == false) {
                
                logger.warn(
                    "Only PBKDF2 is allowed for stored credential hashing in a FIPS 140 JVM. "
                        + "Please set the appropriate value for [{}] setting.",
                    setting.getKey()
                );
            }
        });
        final var cacheHashAlgoSettings = settings.filter(k -> k.endsWith(".cache.hash_algo"));
        cacheHashAlgoSettings.keySet().forEach((key) -> {
            final var setting = cacheHashAlgoSettings.get(key);
            assert setting != null;
            final var hashAlgoName = setting.toLowerCase(Locale.ROOT);
            if (hashAlgoName.equals("ssha256") == false && hashAlgoName.startsWith("pbkdf2") == false) {
                logger.warn(
                    "[{}] is not recommended for in-memory credential hashing in a FIPS 140 JVM. "
                        + "The recommended hasher for [{}] is SSHA256.",
                    setting,
                    key
                );
            }
        });
        if (validationErrors.isEmpty() == false) {
            final StringBuilder sb = new StringBuilder();
            sb.append("Validation for FIPS 140 mode failed: \n");
            int index = 0;
            for (String error : validationErrors) {
                sb.append(++index).append(": ").append(error).append(";\n");
            }