### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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/test/java/org/elasticsearch/xpack/security/authc/ApiKeyServiceTests.java
doAnswer(inv -> {
            final Object[] args = inv.getArguments();
            BulkRequest bulkRequest = (BulkRequest) args[1];
            assertThat(bulkRequest.numberOfActions(), is(1));
            assertThat(bulkRequest.requests().get(0), instanceOf(IndexRequest.class));
            IndexRequest indexRequest = (IndexRequest) bulkRequest.requests().get(0);
            assertThat(indexRequest.id(), is(createApiKeyRequest.getId()));
            
            assertThat(indexRequest.opType(), is(DocWriteRequest.OpType.CREATE));
            bulkActionInvoked.set(true);
            return null;
        }).when(client).execute(eq(BulkAction.INSTANCE), any(BulkRequest.class), any());
        service.createApiKey(authentication, createApiKeyRequest, Set.of(), new PlainActionFuture<>());
        assertBusy(() -> assertTrue(bulkActionInvoked.get()));
    }
    @SuppressWarnings("unchecked")
    public void testGetApiKeys() throws Exception {
        final Settings settings = Settings.builder().put(XPackSettings.API_KEY_SERVICE_ENABLED_SETTING.getKey(), true).build();
        when(client.threadPool()).thenReturn(threadPool);
        SearchRequestBuilder searchRequestBuilder = Mockito.spy(new SearchRequestBuilder(client, SearchAction.INSTANCE));
        when(client.prepareSearch(eq(SECURITY_MAIN_ALIAS))).thenReturn(searchRequestBuilder);
        final ApiKeyService service = createApiKeyService(settings);
        final AtomicReference<SearchRequest> searchRequest = new AtomicReference<>();
        doAnswer(invocationOnMock -> {
            searchRequest.set((SearchRequest) invocationOnMock.getArguments()[0]);
            ActionListener<SearchResponse> listener = (ActionListener<SearchResponse>) invocationOnMock.getArguments()[1];
            listener.onResponse(SearchResponse.empty(() -> 1L, SearchResponse.Clusters.EMPTY));
            return null;
        }).when(client).search(any(SearchRequest.class), anyActionListener());
        String[] realmNames = generateRandomStringArray(4, 4, true, true);