### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.internal.InternalSearchResponse;
import org.elasticsearch.test.ClusterServiceUtils;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.test.MockLogAppender;
import org.elasticsearch.test.TransportVersionUtils;
import org.elasticsearch.test.VersionUtils;
import org.elasticsearch.test.XContentTestUtils;
import org.elasticsearch.threadpool.FixedExecutorBuilder;
import org.elasticsearch.threadpool.TestThreadPool;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.xcontent.NamedXContentRegistry;
import org.elasticsearch.xcontent.ToXContent;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParserConfiguration;
import org.elasticsearch.xcontent.XContentType;
import org.elasticsearch.xcontent.json.JsonXContent;
import org.elasticsearch.xpack.core.XPackSettings;
import org.elasticsearch.xpack.core.security.SecurityContext;
import org.elasticsearch.xpack.core.security.action.ClearSecurityCacheAction;
import org.elasticsearch.xpack.core.security.action.ClearSecurityCacheRequest;
import org.elasticsearch.xpack.core.security.action.ClearSecurityCacheResponse;
import org.elasticsearch.xpack.core.security.action.apikey.AbstractCreateApiKeyRequest;
import org.elasticsearch.xpack.core.security.action.apikey.ApiKey;
import org.elasticsearch.xpack.core.security.action.apikey.ApiKeyTests;
import org.elasticsearch.xpack.core.security.action.apikey.BaseUpdateApiKeyRequest;
import org.elasticsearch.xpack.core.security.action.apikey.BulkUpdateApiKeyRequest;
import org.elasticsearch.xpack.core.security.action.apikey.BulkUpdateApiKeyResponse;
import org.elasticsearch.xpack.core.security.action.apikey.CreateApiKeyRequest;