### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
)
            );
            apiKeyAuthCache.put(idPrefix + count.incrementAndGet(), new ListenableFuture<>());
            appender.assertAllExpectationsMatched();
            appender.addExpectation(
                new MockLogAppender.UnseenEventExpectation(
                    "replace",
                    ApiKeyService.class.getName(),
                    Level.TRACE,
                    "API key with ID [" + idPrefix + "*] was evicted from the authentication cache*"
                )
            );
            apiKeyAuthCache.put(idPrefix + count.get(), new ListenableFuture<>());
            appender.assertAllExpectationsMatched();
            appender.addExpectation(
                new MockLogAppender.UnseenEventExpectation(
                    "invalidate",
                    ApiKeyService.class.getName(),
                    Level.TRACE,
                    "API key with ID [" + idPrefix + "*] was evicted from the authentication cache*"
                )
            );
            apiKeyAuthCache.invalidate(idPrefix + count.get(), new ListenableFuture<>());
            apiKeyAuthCache.invalidateAll();
            appender.assertAllExpectationsMatched();
        } finally {
            appender.stop();
            Loggers.setLevel(logger, Level.INFO);
            Loggers.removeAppender(logger, appender);
        }