Draft: Enable usage of UBI micro as base image

What does this MR do?

Enable usage of UBI micro as base image

Retrieve image sha and set UBI_IMAGE to UBI micro for jobs that have USE_UBI_MICRO set to true.

This prepares CNG to convert images from UBI minimal to UBI micro.

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🗒 CNG already has Dockerfiles that default to UBI micro, but the build arg is overridden to UBI minimal.

Related issues

Relates #1794

Relates #1795

Relates #1796

Relates #1797

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
  • Confirm the latest kubectl build of !1715 is based on UBI micro.
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated
• New dependencies are managed with dependencies.io