Launching or starting a VM fails with "... QEMU failed to run feature checks"

Description:

Launching a new or starting an existing VM fails (since Incus 6.3) with:

Error: Failed instance creation: Failed creating instance record: Instance type "virtual-machine" is not supported on this server: QEMU failed to run feature checks

Additional info:

The reason seems to be that the INCUS_OVMF_PATH environment variable was renamed to INCUS_EDK2_PATH ...

https://discuss.linuxcontainers.org/t/incus-6-3-has-been-released/21019#notice-for-packagers-10

... and the old name is still used in incus.service

Steps to reproduce:

1. incus launch images:ubuntu/22.04 ubuntu-vm --vm fails with the error message above in the bug description
2. Manual fix:
   • # systemctl edit --full incus.service
     • Change Environment=INCUS_OVMF_PATH=/usr/share/ovmf/x64 to Environment=INCUS_EDK2_PATH=/usr/share/ovmf/x64
   • Restart service: # systemctl restart incus.service
   • Now incus launch images:ubuntu/22.04 ubuntu-vm --vm works as expected