redhatsignedrpmcheck: Add remediation hint and URL

[pirat89]

Users do not have an idea what they should do about the third party packages - and quite often they do not understand the report itself. Adding the remediation hint with a link to related KB solution to help them to understand what they can do about this.

Note the actor needs significant changes to cover also other non-RHEL distributions. I decided to keep the change simple and resolve that in a follow up when we enable upgrades on other distributions as well.

jira: RHEL-44596

[github-actions]

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