Upgrade to Drupal 10

Drupal:
- remove acquia/blt
- upgrade to the latest Drupal 9
- replace or remove deprecated modules
- upgrade to ckeditor5
- make sure that custom code and themes are drupal 10 compatible
- make sure that contrib modules are drupal 10 compatible
- upgrade Drupal core

Tooling:
- replace lando with ddev
- upgrade drush