feat: enable Artifact Streaming on Flatcar

[chewi]

What type of PR is this?

/kind cleanup /kind feature

What this PR does / why we need it:

Artifact Streaming is an important feature for Flatcar.

This uses Flatcar's own systemd system extension for overlaybd and Azure Linux's RPM for acr and the configuration scripts. It's not perfect, but we cannot improve on this until acr changes its build process or goes open source.

Which issue(s) this PR fixes:

Fixes Flatcar for AKS work item #34435545

Requirements:

• [X] uses conventional commit messages
• [ ] includes documentation
• [ ] adds unit tests
• [ ] tested upgrade from previous version
• [X] commits are GPG signed and Github marks them as verified

Release note:

* Enabled Artifact Streaming on Flatcar.