[svirt][serial][xen] Enable svirt serial console for XEN
Svirt serial console has been enabled only for s390x, used mainly for LTP tests.
It'd be good to enable it for other archs, let's start with XEN as it was requested.
See PR, which needs debugging and finding valid libvirt code part
Fixes for original implementation for s390x (#45863)
Some related PR to understand the code a bit
https://github.com/os-autoinst/os-autoinst/pull/1154 (logging xml file in autoinst-log.txt)
NOTE: it's not working on Hyper-V and VMware either.
This ticket was set to "Normal" priority but was not updated within the SLO period for "Normal" tickets (365 days) as described on https://progress.opensuse.org/projects/openqatests/wiki/Wiki#SLOs-service-level-objectives . Please consider picking up this ticket within the next 365 days or just set the ticket to the next lower priority of "Low" (no SLO related time period). This update was done as agreed within the SUSE QE Sync call 2021-09-01