### Description

The [Get API key information API](https://www.elastic.co/guide/en/elasticsearch/reference/master/security-api-get-api-key.html) can currently filter the returned keys by:
 * key id/name
 * keys owned by the calling user
 * keys owned by other users, by `realm_name` and `username`

Irrespective of the filtering used, both invalidated and expired (but not yet deleted) keys will be included in the response.
In the response, keys have the `invalidated` boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.

I propose we introduce a way for the API to support retrieving:
* only valid API keys (not return invalidated keys) - using a boolean request parameter
* keys not expired before a certain timestamp - using a timestamp parameter that defaults to "now" - also note that keys' experiation date is always checked against the local node's clock
x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/ApiKeyServiceTests.java
);
            appender.addExpectation(
                new MockLogAppender.UnseenEventExpectation(
                    "throttling",
                    ApiKeyService.class.getName(),
                    Level.WARN,
                    "Possible thrashing for API key authentication cache,*"
                )
            );
            apiKeyAuthCache.put(randomAlphaOfLength(23), new ListenableFuture<>());
            appender.assertAllExpectationsMatched();
        } finally {
            appender.stop();
            Loggers.setLevel(logger, Level.INFO);
            Loggers.removeAppender(logger, appender);
        }
    }
    public void testAuthenticateWhileCacheBeingPopulated() throws Exception {
        final String apiKey = randomAlphaOfLength(16);
        Hasher hasher = getFastStoredHashAlgoForTests();
        final char[] hash = hasher.hash(new SecureString(apiKey.toCharArray()));
        Map<String, Object> sourceMap = buildApiKeySourceDoc(hash);
        final Object metadata = sourceMap.get("metadata_flattened");
        final ApiKey.Type type = parseTypeFromSourceMap(sourceMap);
        ApiKeyService realService = createApiKeyService(Settings.EMPTY);
        ApiKeyService service = Mockito.spy(realService);
        
        
        final Semaphore hashWait = new Semaphore(0);
        final AtomicInteger hashCounter = new AtomicInteger(0);