Move to GitLab CI

One part of the tests is causing a problem, although I am puzzled by the apparent Drupal CI result that seems to suggest it is still working. It is this code fragment from Functional/WhoopsTest:

    // Ensures that HttpExceptions not handled by exception subscribers
    // registered before the whoops exception subscriber (e.g when the format
    // is unknown) are caught and reported as whoops error page and the http
    // status code is preserved.
    $this->drupalGet('not-exist', ['query' => ['_format' => 'mhe']]);
    $this->assertSession()->statusCodeEquals(404);
    // This assertion is intentionally shorter than the full text because
    // Drupal 9 and Drupal 10 have slightly different messages.
    $this->assertWhoopsErrorPage('No route found for "GET');

I'll remove that for now and create a new issue to see if it should be restored. It seems reasonable behaviour that a 404 simply loads the 404 page and does not show a Whoops screen.

Automatically closed - issue fixed for 2 weeks with no activity.