cfg2cmd: switch off ACPI hotplug on bridges for q35 VMs

cfg2cmd: switch off ACPI hotplug on bridges for q35 VMs

See commit 17858a1695 (hw/acpi/ich9: Set ACPI PCI hot-plug as default
on Q35)[0] in upstream QEMU repository for details about why the change
was made.

As that change affects systemds predictable interface naming[1],
e.g., by going from a previously `ens18` name to `enp6s18`, it may
have rather bad effects for users that did not setup some .link files
to enforce a specific naming by an more stable information like the
NIC's MAC-Address

The alternative would be making the preferred mode of hotplug an
option like `hotplug-mode=<acpi|pcie>`, but it does not seems like
one would like to change that much in the first place...

Note the changes to the tests and especially the tests with q35
machines that did not change.

[0]: https://gitlab.com/qemu-project/qemu/-/commit/17858a1695
[1]: https://www.freedesktop.org/software/systemd/man/systemd.net-naming-scheme.html#Naming

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Acked-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Reviewed-by: Dominik Csapak <d.csapak@proxmox.com>
Tested-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>