After first release from `bazel` build, remove artifacts which were used in the old release process

[filmil]

Prerequisite: At least one bazel build based release process, governed by the release-please action must have already successfully been completed.

This includes, but is not limited to:

• docker container definitions of the build environments
• the versioning metadata (files LAST_RELEASED_VERSION and NEXT_VERSION)
• Makefiles
• The GitHub workflows relying on Makefiles and docker.
  • When modifying the workflows, adapt the status badges for the builds in README.md