Update automated testing configuration

Update the automated testing configuration. Remove tests for 8.x-3.x, which is unsupported. Remove tests for Drupal 9, which is unsupported. Add more tests, such as PHP 8.1 and other databases.

For Drupal 7, since it now requires PHP 5.6, testing for that should take priority over PHP 5.3. It would also be nice to add other databases.