Description
Drupal is using Symfony's PHPUnit bridge to detect usages of deprecated code during tests. This has proved amazing useful in managing our technical debt and has helped us prepare for Symfony 4 and 5. One problem we've faced because of Drupal's size is that it is not always possible to address new deprecations at the same time as upgrading a dependency. In order to handle this we've added the ability to skip specific deprecations which we can then handle in a separate issue.

When skipping a deprecation we can either match the entire message or use a regex for a dynamic deprecation message.

Example
For example, Drupal 9 is using Symfony 4 and we're skipping the The "Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesser" class is deprecated since Symfony 4.3, use "Symfony\Component\Mime\MimeTypes" instead. deprecation notice and handling the changes we need to make to Drupal in https://www.drupal.org/project/drupal/issues/3055193