Draft: feat(15_rhel): implement yum update testing

[fujexo]

This extends the RHEL checks by a dry-run yum update -y to verify if the updates will be applied or report if there are errors.

[Melkor333]

In my opinion this is ovrefluous, since we do have some checks for yum now that work and the yum update has to be run manually anyway.
But in case we still want to merge this, It should be first tested on centos 7-9, because with all other yum checks we had some problems with breaking changes in between versions