### 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boolean property, as well as the `expiration` property that contains the UNIX timestamp past of which the key is no longer valid for authentication.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
PlainActionFuture<AuthenticationResult<User>> future = new PlainActionFuture<>();
        service.loadApiKeyAndValidateCredentials(threadContext, apiKeyCredentials, future);
        assertNull(service.getApiKeyAuthCache().get(docId));
    }
    public void testGetCreatorRealm() {
        final User user = AuthenticationTests.randomUser();
        
        final String apiKeyId = randomAlphaOfLength(20);
        final Authentication authentication1 = AuthenticationTests.randomApiKeyAuthentication(user, apiKeyId);
        assertThat(ApiKeyService.getCreatorRealmName(authentication1), equalTo(AuthenticationField.API_KEY_CREATOR_REALM_NAME));
        assertThat(ApiKeyService.getCreatorRealmType(authentication1), equalTo(AuthenticationField.API_KEY_CREATOR_REALM_TYPE));
        
        final RealmRef lookupRealmRef = AuthenticationTests.randomRealmRef(false);
        final Authentication authentication2 = authentication1.runAs(AuthenticationTests.randomUser(), lookupRealmRef);
        assertThat(ApiKeyService.getCreatorRealmName(authentication2), equalTo(lookupRealmRef.getName()));
        assertThat(ApiKeyService.getCreatorRealmType(authentication2), equalTo(lookupRealmRef.getType()));
        
        final Authentication authentication3 = AuthenticationTests.randomRealmAuthentication(randomBoolean());
        assertThat(ApiKeyService.getCreatorRealmName(authentication3), equalTo(authentication3.getEffectiveSubject().getRealm().getName()));
        assertThat(ApiKeyService.getCreatorRealmType(authentication3), equalTo(authentication3.getEffectiveSubject().getRealm().getType()));
        
        final Authentication authentication4 = authentication3.runAs(AuthenticationTests.randomUser(), lookupRealmRef);
        assertThat(ApiKeyService.getCreatorRealmName(authentication4), equalTo(lookupRealmRef.getName()));
        assertThat(ApiKeyService.getCreatorRealmType(authentication4), equalTo(lookupRealmRef.getType()));
        
        final Authentication authentication5 = randomFrom(
            AuthenticationTests.randomServiceAccountAuthentication(),
            AuthenticationTests.randomAnonymousAuthentication(),
            AuthenticationTests.randomInternalAuthentication()
        );