### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
private final String id;
        private final SecureString key;
        private final ApiKey.Type expectedType;
        public ApiKeyCredentials(String id, SecureString key, ApiKey.Type expectedType) {
            this.id = id;
            this.key = key;
            this.expectedType = expectedType;
        }
        String getId() {
            return id;
        }
        SecureString getKey() {
            return key;
        }
        @Override
        public void close() {
            key.close();
        }
        @Override
        public String principal() {
            return id;
        }
        @Override
        public Object credentials() {
            return key;
        }