Package Pipeline: the "Plan" stage should provide direct link to the artifacts/page to test

[dduportal]

From jenkins-infra/helpdesk#4774 (comment)

The "Plan" stage should help the release lead by providing direct links to the 4 elements to check (Debian, RPM for RH/openSUSE, WAR and Windows): they don't care about the "staging pkg uses subdomains and redirects to staging get.jio only for binaries" which is an infra-only stuff. But since this architecture is required, let's ease their life.

• We expect only 4 links as far as I can tell
• The RELEASELINE environment variable should be used: it's empty on the weekly line and set to -stable on LTS line
• The links to the WAR and MSI directories in the "staging.get.jenkins.io" webservice should be provided to ensure operator can download the file for test, but also download the checksums (or any future GPG signature) file
• The links to the RPM and Debian web pages on the ".staging.pkg.origin.jenkins.io" webservice should be provided to ensure operator can follow instructions to test the packages on Debian, Ubuntu, RedHat, openSUSE, Fedora, etc. with only copy and paste