feat: add universe domain support

[bshaffer]

• add tests
• E2E manual test
• Support for GOOGLE_CLOUD_UNIVERSE_DOMAIN environment variable
• Support universe domain in Batch

See also googleapis/google-api-php-client-services#4675

The following manual test worked using this branch:

$universeDomain = 'MY_UNIVERSE_DOMAIN';
$projectId = 'MY_PROJECT_ID';

$client = new Google\Client([
    'universe_domain' => $universeDomain,
    'scopes' => ['https://www.googleapis.com/auth/cloud-platform'],
]);
$client->useApplicationDefaultCredentials();
$storage = new Google\Service\Storage($client);

$buckets = $storage->buckets->listBuckets($projectId);

foreach ($buckets as $bucket) {
    echo $bucket->name . PHP_EOL;
}