### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
this.type = type;
            this.creationTime = creationTime;
            this.expirationTime = expirationTime;
            this.invalidated = invalidated;
            this.hash = hash;
            this.name = name;
            this.version = version;
            this.creator = creator;
            this.roleDescriptorsHash = roleDescriptorsHash;
            this.limitedByRoleDescriptorsHash = limitedByRoleDescriptorsHash;
            this.metadataFlattened = metadataFlattened;
        }
        public ApiKeyDoc toApiKeyDoc(BytesReference roleDescriptorsBytes, BytesReference limitedByRoleDescriptorsBytes) {
            return new ApiKeyDoc(
                "api_key",
                type,
                creationTime,
                expirationTime,
                invalidated,
                hash,
                name,
                version,
                roleDescriptorsBytes,
                limitedByRoleDescriptorsBytes,
                creator,
                metadataFlattened
            );
        }
    }
    private static final class ApiKeyDocCache {