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* Optimize container images for startup

This change adjusts how to handle runner payloads to support
container builds where we keep them extracted in the filesystem.
This makes it easier to optimize the cpu/cuda vs cpu/rocm images for
size, and should result in faster startup times for container images.

* Refactor payload logic and add buildx support for faster builds

* Move payloads around

* Review comments

* Converge to buildx based helper scripts

* Use docker buildx action for release

Flesh out our github actions CI so we can build official releaes.

Allow overriding the platform, image name, and tag latest for
standard and rocm images.

This adds ROCm support back as a discrete image.

If a VERSION is not specified, this will generate a version string that
represents the state of the repo.  For example `0.1.21-12-gffaf52e1-dirty`
representing 12 commits away from 0.1.21 tag, on commit gffaf52e1
and the tree is dirty.