Use cloud-hypervisor for net-vm on x86

[slakkala]

Description of changes

Replace QEMU with cloud-hypervisor for net-vm guest on x86 hardware.

cloud-hypervisor makes a differently connected virtual device, so the permanent name of the interface changes.

Move smcroute startup to NetworkManager dispatcher script to allow the guest to reach multi-user.target before host timeout reboots the VM.

Checklist for things done

• [X] Summary of the proposed changes in the PR description
• [ ] More detailed description in the commit message(s)
• [X] 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:
  • [X] 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

Verify that network connectivity works after configuring it.