AudioVM and client configuration with separate VM audio chennels

[josa41]

Description of changes

AudioVM configuration which adds Audio IO channels for VMs (per confiugration).
Clean up of AppVM configuration to add client audioVM connections based on VM name

Checklist for things done

• [X ] Summary of the proposed changes in the PR description
• [X ] 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
• [X ] 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
• [X ] 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

[mbssrc]

Can we use lingering (see below) instead of the pulseaudio-starter service?

systemd.tmpfiles.rules = [
  "f /var/lib/systemd/linger/${config.ghaf.users.accounts.user}"
];

[mbssrc]

I suppose that we want to aim at dynamic support, i.e., supporting several input/output devices such as bluez_input/output, starting with auto-switch and later selection.