Have ko publish multi-arch builds, drop Dockerfile

[mattmoor]

Description

@dekkagaijin pointed me at: https://github.com/sigstore/cosign/blob/fbe6fabcf3dbad1f94e1fd50d3bbe157c180b5be/.goreleaser.yml#L162-L232

We can just publish images like we do for /ci/, but with --platform=all to build for ~5 architectures.

There are examples of doing this as part of a release workflow with goreleaser here: https://github.com/mattmoor/mink/blob/master/.github/workflows/release.yaml (attaching the release yaml to the release @n3wscott 👀 )

[mattmoor]

cc @dlorenc @cpanato

[mattmoor]

One thing @dlorenc brought up that might be problematic with ko is the piv-key stuff, which uses cgo

[cpanato]

@mattmoor @dlorenc the idea is to use ko and drop goreleaser for building the images? and how about the binaries?

we can drop goreleaser and use a make/bash that builds everything and push to github.

we just need to decide how we move forward and I can implement the changes

One thing @dlorenc brought up that might be problematic with ko is the piv-key stuff, which uses cgo

for this we are only building the binaries not images

[cpanato]

ignore the issue link, copy/paste issues

[dlorenc]

Done in #984!