Reimplement git-repo-scanner in Go #3378

Since we've lost our pythonic maintainers it is hard to maintain this particular scanner. We decided to try a reimplementation in Go, so we have less language ecosystems to maintain.

First we need to doa short discovery how much effort this will be to decide, if follow this path.

At a first glance it seems doable since the scanner has roughly 4 Python files with roundabout 700 LOC in total.