We recently updated the release process on main, but this targeted main after the last hotfix which had temporarily reverted code. Specifically it undid #425 which unified the pbs, signer, and cli binaries into just commit-boost. Since the new release process didn't include these changes, this PR captures them.

Specifically, we're introducing a new commit-boost Docker image to the release process that defaults to use the pbs command. This is the new de facto image used throughout the project, including the Justfile. However, to remain backwards compatible, each release will continue to ship a pbs:latest and signer:latest image, which are simply clones of the commit-boost image but hardwired to use their pbs and signer commands respectively.