### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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/main/java/org/elasticsearch/xpack/security/authc/ApiKeyService.java
final MessageDigest digest = MessageDigests.sha256();
            final String roleDescriptorsHash = MessageDigests.toHexString(MessageDigests.digest(roleDescriptorsBytes, digest));
            digest.reset();
            final String limitedByRoleDescriptorsHash = MessageDigests.toHexString(
                MessageDigests.digest(limitedByRoleDescriptorsBytes, digest)
            );
            return new CachedApiKeyDoc(
                type,
                creationTime,
                expirationTime,
                invalidated,
                hash,
                name,
                version,
                creator,
                roleDescriptorsHash,
                limitedByRoleDescriptorsHash,
                metadataFlattened
            );
        }
        static ApiKeyDoc fromXContent(XContentParser parser) {
            return PARSER.apply(parser, null);
        }
    }
    /**
     * A cached version of the {@link ApiKeyDoc}. The main difference is that the role descriptors
     * are replaced by their hashes. The actual values are stored in a separate role descriptor cache,
     * so that duplicate role descriptors are cached only once (and therefore consume less memory).
     */
    public static final class CachedApiKeyDoc {