Setup RE cache server to use with buildstream master (in preparation to switch to buildstream 2.0)
Buildstream master supports Remote Execution protocols (https://github.com/bazelbuild/remote-apis), so we can use a RE server implementation as a cache server, instead the buildstream-only bst-artifact-server.
Prefered option would be buildbarn (https://github.com/buildbarn/bb-storage/) as we have experience with is and is proved to work in high demanding scenarios