Change build process to use busybox

[gcleroux]

Description of Changes

@coutug and I worked on Kubernetes Jobs for the sink. He needs a shell running inside the container to be able to synchronize workloads to order steps inside the job.

• Compile to a static binary
• Using -ldflag "-s -w" compile flags to reduce the binary size
• Switch the runner image from distroless-base to distroless-static
• Building the image inside the Dockerfile instead of GitHub Action
• Copying a static /bin/sh shell and /bin/touch inside the distroless image (needed for the helm chart job)

Build Sizes

Build process	Image Size
Distroless base w/ no shell	95.60 MB
Distroless static w/ /bin/sh	57.37 MB

Some Questions

I'm running the build step inside the Dockerfile with build-args to keep the resulting binary the same. The metadata action uses a slightly different date format
e.g. "2024-07-30T22:06:23.354Z" instead of "2024-07-30T22:06Z"

I assumed it was fine and didn't change it, but I can format it like the action if needed.

[fschoell]

otherwise lgtm