We need to adjust convert2rhel code so that conversions to RHEL 9 work are as seamless as conversions to RHEL 7 and 8.

The source OSes we focus on: Rocky, Alma, Oracle.

Acceptance criteria:

• convert2rhel is updated to allow conversions of Rocky/Alma/Oracle 9 to RHEL 9
  • The pattern is the same as with RHEL 8 - the latest minor version and all minor versions that correspond to RHEL 9 minor versions with active EUS.
    • Except Oracle Linux - that is a rolling distro that does not have older minor version repos => we'll support conversions from the OL9 latest only.
  • Example of minor versions to allow converting:
    • Rocky/Alma 9.0 and 9.2 (both corresponding to active RHEL 9 EUS releases)
    • Rocky/Alma/Oracle 9.3 (latest)
• convert2rhel upstream CI is set up to run conversion tests on Rocky/Alma/Oracle 9 for every upstream change before it's merged
• the documentation is updated