Make dbup compatible with php 8.1

[ymauray]

This pull request makes dbup compatible with php 8.1 Also, phpcs, phpstan, and phpmd are now happy with the source code.

[Arcantel]

Also :

• upgraded all the dependencies and dev dependencies
• upgraded all tests
• moved files around in the tests folder
• removed some unneccessay or unused files in the tests folder
• added scripts to composer.json to run unit tests using composer phpunit