Add support for org.osbuild.rhsm osbuild stage

Add support for org.osbuild.rhsm osbuild stage. This stage is available in osbuild since version 24. The stage currently allows only configuring the enablement status of two RHSM DNF plugins, specifically of product-id and subscription-manager DNF plugins.

RHEL 8.3 & 8.4: Disable all RHSM DNF plugins on qcow2 image

Disable both available RHSM DNF plugins (product-id and subscription-manager) on rhel-8 and rhel-84 qcow2 images. The reason for disabling these DNF plugins is to make the produced images consistent in this regard, with what had been previously produced by the imagefactory.