### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
.setId(request.getId())
                        .setOpType(DocWriteRequest.OpType.CREATE)
                        .request()
                );
                bulkRequestBuilder.setRefreshPolicy(request.getRefreshPolicy());
                final BulkRequest bulkRequest = bulkRequestBuilder.request();
                securityIndex.prepareIndexIfNeededThenExecute(
                    listener::onFailure,
                    () -> executeAsyncWithOrigin(
                        client,
                        SECURITY_ORIGIN,
                        BulkAction.INSTANCE,
                        bulkRequest,
                        TransportBulkAction.<IndexResponse>unwrappingSingleItemBulkResponse(ActionListener.wrap(indexResponse -> {
                            assert request.getId().equals(indexResponse.getId());
                            assert indexResponse.getResult() == DocWriteResponse.Result.CREATED;
                            final ListenableFuture<CachedApiKeyHashResult> listenableFuture = new ListenableFuture<>();
                            listenableFuture.onResponse(new CachedApiKeyHashResult(true, apiKey));
                            apiKeyAuthCache.put(request.getId(), listenableFuture);
                            listener.onResponse(new CreateApiKeyResponse(request.getName(), request.getId(), apiKey, expiration));
                        }, listener::onFailure))
                    )
                );
            } catch (IOException e) {
                listener.onFailure(e);
            } finally {
                Arrays.fill(apiKeyHashChars, (char) 0);
            }
        }));
    }