### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
public void updateApiKeys(
        final Authentication authentication,
        final BaseBulkUpdateApiKeyRequest request,
        final Set<RoleDescriptor> userRoleDescriptors,
        final ActionListener<BulkUpdateApiKeyResponse> listener
    ) {
        assert request.getType() != ApiKey.Type.CROSS_CLUSTER || userRoleDescriptors.isEmpty()
            : "owner user role descriptor must be empty for cross-cluster API keys";
        ensureEnabled();
        if (authentication == null) {
            listener.onFailure(new IllegalArgumentException("authentication must be provided"));
            return;
        } else if (authentication.isApiKey()) {
            listener.onFailure(
                new IllegalArgumentException("authentication via API key not supported: only the owner user can update an API key")
            );
            return;
        }
        final TransportVersion transportVersion = getMinTransportVersion();
        if (transportVersion.before(TRANSPORT_VERSION_ADVANCED_REMOTE_CLUSTER_SECURITY_CCS)
            && hasRemoteIndices(request.getRoleDescriptors())) {
            
            listener.onFailure(
                new IllegalArgumentException(
                    "all nodes must have transport version ["
                        + TRANSPORT_VERSION_ADVANCED_REMOTE_CLUSTER_SECURITY_CCS
                        + "] or higher to support remote indices privileges for API keys"
                )
            );
            return;