This fixes #1998 where with some checking it seems Bullseye has some
issues with the glibc sleep call. It returns a SIGILL.
The glibc on Buster doesn't seem to have this issue, so revert back for
now until a fix has been released.
- Split Debian and Alpine into different build matrix
This starts building both Debian and Alpine based images at the same time
- Make use of Docker BuildKit, which improves speed also.
- Use BuildKit caching for Rust Cargo across docker images.
This prevents downloading the same crates multiple times.
- Use Github Actions Services to start a docker registry, starting it
via the build script sometimes caused issues.
- Updated the Build workflow to use Ubuntu 20.04 which is more close to
the Bullseye Debian release regarding package versions.
