Adding Athena OS test cases

[D3vil0p3r]

What would you like to be added:
We would like to add Athena OS test cases:

• test_boot_to_live_environment
• test_install_athena_arch_entire_disk_with_defaults
• test_install_athena_nix_entire_disk_with_defaults
• test_post_install_clean_first_run

Why is this needed:
To implement quicktest for Athena OS in CI/CD workflows to keep the OS periodically monitored for successful installation.

[AkechiShiro]

I'll try to check how other checks are made and see if it is possible for me to implement these checks with a PR