Integration of nvd-mirror into gitlab-depscan

Related to gitlab-org/gitlab#222821 (closed)

This is a reimplementation of gitlab-depscan. The previous implementation was pretty much tied to cve-search which we replaced with nvd-mirror.

Due to this shift we had to replace large portions of the implementation anyway. Therefore, it was a cleaner solution to reimplement gitlab-depscan in a way that is consistent with the other analyzers we use (using our common library) and the most recent report format.