choco sync --source functionality

There's no way to use choco sync for internal repos, only the global repo.

Additionally, automatic sync doesn't work for internal repos, I believe this is caused by choco sync not working with internal repos, but I created separate issue 2327 for this

Start with the `choco sync --source` command and review issue 2327 for the related automatic-sync behavior. The work is done when sync supports internal repositories as well as the global repository, including the automatic-sync case described here.

Written by the indexing model from the issue text.