chore: follow-up of UBI9 image introduction

[lemeurherveCB]

This PR adds the rhel-ubi9 target in the docker-bake.hcl groups definitions so the corresponding images are built and published.

It also add an updatecli manifest to keep UBI9_TAG up to date in the Dockerfile and in docker-bake.hcl, and it updates the README.md

Follow-up of:

• [JENKINS-73703] Add agent images for UBI 9 #866

Testing done

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