Improve log collection for consolebase based tests and systemd enabled services

[foursixnine]

opensusebasetest: Update the flow of error detection mechanism consoletest: Use serial terminal after parent's post_fail_hook

At the moment, if the SUT is using a serial terminal, we simply return, and let the rest of the post-fail-hook to do the work, so if the child (e.g consoletest) doesn't call export_logs() or doesn't do any specific actions, export_logs_basic will be called, and these logs aren't really providing much.

VR: https://openqa.suse.de/tests/6594648#

A bit more testing is needed, to cover arches that don't have serial terminal too

Extra commits are from: #12990