4.1.0: rework Dockerfile and add clang dev tools

Besides the refactor of the Dockerfile focused on rebuild efficiency done by @EinarElen in #67 , we also included a few more clang development tools as well as fixed the building workflow which was putting all of the previous digests into the manifest for an image rather than just the two from its workflows.

What's Changed

• 66 somethings wrong with the dockerhub setup by @tomeichlersmith in #68
• Iss65 split packages by @EinarElen in #67

Full Changelog: v4.0.1...v4.1.0