Attempt to debloat/modularize tests

[avnik]

Description

Proof of concept to splitting out test VM configs.
After recent rebasing to master it start fail test, so need to be fixed/re-done.
This PR was done for discussion/inspiration how we could improve tests.

Checklist

• Summary of the proposed changes in the PR description
• More detailed description in the commit message(s)
• Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• Contribution guidelines followed
• Test procedure added to nixos/tests
• Author has run nix flake check --accept-flake-config and it passes
• All automatic Github Action checks pass - see actions
• Author has added reviewers and removed PR draft status

Testing