Runner build should produce and publish containers

[bryanmacfarlane]

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Describe the enhancement
Every runner build should produce containers and they should be published. This allows for kubernetes or other container services to elastically run jobs with the latest runner (avoiding the need for potential updates when starting)

Additional information
Would be nice to have standard linux distros as well as alpine

NOTE: if the feature request has been agreed upon then the assignee will create an ADR. See docs/adrs/README.md

[nikola-jokic]

Happy to say we can close this issue now, since this PR has been merged, and building images is part of the release process now ☺️