v5.1.2 Usher dependency updates
This updates Usher as follows:
- actions/checkout@v4 to actions/checkout@v6
- shivammathur/setup-php@2.32.0 to shivammathur/setup-php@2.36.0
- async/aws free to move to v3
- symfony/yaml free to move to v8
- Adds drupal/core-composer-scaffold plugin
- A minor Phpstan/rector fix.
Updates the README to remove support for Drupal 10.0 and below.