Refactor pipeline

This merge request is a rewrite of the actual pipeline used for the daily scheduled build of the bob stack.

Rather than relying on complex scripts that requires fiddling to ensure that the environment are clean between package builds and other elements, it takes advantage of the downstream pipelines concept from GitLab.

In this case, these will be project pipelines which means that each package will run its own usual pipeline and in case of failure, there will be two messages: one for the nightlies and one for the package(s) that failed their pipeline run.

One interesting benefit is that some of the builds can be parallelized as not all bob packages relies on the same core packages. Another one is that this pipeline becomes lighter weight as it is now essentially a list of projects to build. All of this should help reduce the resources required as well as the time it takes to run a full build.

The content of the file is based on the order.txt content with parallelism introduced where it makes sense. For example all bob.bio. packages can be built at the same time once bob/bob.bio.base> is done as they don't rely on each other.