Allocate appvm mac addresses automatically

[remimimimimi]

Description of changes

This PR implements an allocator for appvm’s MAC addresses and their collision detector, following current convention “02:00:00:03:{n}:01”. Allows up to 256 addresses to be assigned automatically.

Checklist for things done

• 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
• Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• PR linked to architecture documentation and requirement(s) (ticket id)
• Test procedure described (or includes tests). Select one or more:
  • Tested on Lenovo X1 x86_64
  • Tested on Jetson Orin NX or AGX aarch64
  • Tested on Polarfire riscv64
• 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

Installed lenovo-x1-gen-11-debug image on the hardware and tried to run virtual machines.