### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
assertTrue(result.isAuthenticated());
        assertThat(result.getValue().principal(), is("test_user"));
        assertThat(result.getValue().fullName(), is("test user"));
        assertThat(result.getValue().email(), is("test@user.com"));
        assertThat(result.getValue().roles(), is(emptyArray()));
        assertThat(result.getValue().metadata(), is(Collections.emptyMap()));
        assertThat(result.getMetadata().get(AuthenticationField.API_KEY_ROLE_DESCRIPTORS_KEY), equalTo(apiKeyDoc.roleDescriptorsBytes));
        assertThat(
            result.getMetadata().get(AuthenticationField.API_KEY_LIMITED_ROLE_DESCRIPTORS_KEY),
            equalTo(apiKeyDoc.limitedByRoleDescriptorsBytes)
        );
        assertThat(result.getMetadata().get(AuthenticationField.API_KEY_CREATOR_REALM_NAME), is("realm1"));
        assertThat(result.getMetadata().get(API_KEY_TYPE_KEY), is(apiKeyDoc.type.value()));
        apiKeyDoc = buildApiKeyDoc(hash, Clock.systemUTC().instant().minus(1L, ChronoUnit.HOURS).toEpochMilli(), false);
        future = new PlainActionFuture<>();
        service.validateApiKeyCredentials(
            apiKeyId,
            apiKeyDoc,
            getApiKeyCredentials(apiKeyId, apiKey, apiKeyDoc.type),
            Clock.systemUTC(),
            future
        );
        result = future.get();
        assertNotNull(result);
        assertFalse(result.isAuthenticated());
        
        apiKeyDoc = buildApiKeyDoc(hash, -1, true);
        service.getApiKeyAuthCache().put(apiKeyId, new ListenableFuture<>());
        assertNotNull(service.getApiKeyAuthCache().get(apiKeyId));
        future = new PlainActionFuture<>();