add more features: sync and local test runner

[JosteinLindhom]

This issue was copied from quickfeed/quickfeed#1265

The following are some missing features of the current cm tool; we still rely on rsync for synchronizing.

• support synchronizing from the base repository to the assignments repository
• support synchronizing from the base repository to the tests repository
• support synchronizing from the base repository to the info repository
• support running tests locally using docker; should replace the old qcm tool. It should clone the repositories needed into the docker image etc.

Ideas for the API:

cm sync -assignments lab2
cm sync -assignments lab1 lab2
cm sync -tests lab2
cm sync -tests lab1 lab2
cm sync -info
cm run -repo meling-labs -tests lab2

This should replace most of the Justfile/Makefile targets we currently have. That is, we should integrate the various cm tools that we run before/after synchronizing (see the Justfile for examples, e.g., cm remove-solution-tags.) Or at least, we should provide a flag to run the extra stuff...