[WIP] Upgrade Dockerfile to UBI9

[bdunne]

TODO:

• [ ] Code changes to work with Ruby 3
• [ ] Testing

[miq-bot]

This pull request has been automatically marked as stale because it has not been updated for at least 3 months.

If these changes are still valid, please remove the stale label, make any changes requested by reviewers (if any), and ensure that this issue is being looked at by the assigned/reviewer(s)

Thank you for all your contributions! More information about the ManageIQ triage process can be found in the triage process documentation.

[Fryguy]

@bdunne Did you actually run the bot locally to see if things work? I know that not all of the functionality is covered by tests

[miq-bot]

Checked commits https://github.com/bdunne/miq_bot/compare/3b837d05e550407c413b1acd0b6effd21424e2b1~...5565af400afeb0d47f51f5c0e1d5bbb3208dc26c with ruby 2.7.8, rubocop 1.56.3, haml-lint 0.51.0, and yamllint 8 files checked, 1 offense detected

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• [ ] :bomb: :boom: :fire: :fire_engine: - Linter/Yaml - missing config files