Some apt repos (google-cloud-sdk) have multiple versions of the same
package, so we should support that. Now we do. Also added the
google-cloud-cli-bin package.
Adds a new `checkout` step intended to replace `git checkout` by
actually checking out the correct revision when running commands.
Adds a new `upload_artifact` step that uploads an artifact to a package
specific prefix. Primarily intended for supporting Go dependency
archives, but could also be used for anything.
Added `net-vpn/tailscale` using this new functionality.
