Jest for all

Previously tests for db-manager and cli weren't run, as their package.jsons didn't contain a test script (which lerna would call). This makes sure that those tests run. It additionally sets up the configuration in a way that should provide monorepo-wide coverage information that can be used in MRs. This, however, shows up as unknown at this time, probably due to a bug with Jest (where the projects feature that we're using is still quite young).