Enable proper GitHub codespace in-tree config + novnc to propel better testing/collaboration + Heads qemu headless board

[tlaurion]

First steps are

• reproducing No virtualization is available in a HVM qube QubesOS/qubes-issues#4104 (comment) on top of debian-12 to have swtpm + swtpm-tools ready to go
• bind with novnc which triggers proper port-forwarding poiinting to codepace dns for users to simply connect
• build proper container to minimize prepare time + testing
• try to force 4cpu + 16gb ram workspace.

Context:

• QubesOS won't enable nested virt.
  • Discussed at https://forum.qubes-os.org/t/xen-kvm-nested-virtualization-for-testing/20759/6. Made upstream issue unlocked:
    • Reeopened issue at No virtualization is available in a HVM qube QubesOS/qubes-issues#4104 (comment)
    • Issue reclosed.

Discussion stalled at https://forum.qubes-os.org/t/xen-kvm-nested-virtualization-for-testing/20759/11

[tlaurion]

Some traces since holidays happened in the middle of my tests.

• WiP at master...tlaurion:heads:codespace_test
• Was successful doing a novnc setup over cospace, but qemu with vnc binding required passphrase entered under qemu in monitor mode. Need to find a woraround otherwise novnc binding over portforwarding is simply broken.