Multiarch (amd64,arm64) Operator image

What does this MR do?

Build and publish arm64 container image

Build and publish arm64 container image by using a Kubernetes buildx
driver in CI.

By default multi-arch builds are disabled, and need to be configured
in the project settings.

Changelog: added

This MR uses the approach and scripts from gitlab-org/build/CNG!1425 (merged).

Note: Reconciliation of the GitLab CR in an arm cluster depends on Support multiple architecture build for CNG images (gitlab-org/charts/gitlab#2899).

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
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.

Related issues

Relates #1398