[FR] Push dist/gcp/*.sha256 files to public repo when building releases for GCP

[roscoejp]

It looks like the ./production/packaging/build_and_test_all_in_docker script creates artifacts in the dist/gcp directory that includes *.sha256 files for the binary hashes of a particular build.

If these hash files were uploaded to the repo when a public release is created, they could be used for direct comparison against local/operator built images. This would make public validation of Google's provided hashes a bit easier compared to the current method of scraping the release notes.

[dankocoj-google]

Good idea Roscoe, I'll work on this. We'll also probably publish artifacts in a format like
<service_name>.<aws|gcp>.hash