codeintel: optionally return 1 row per package name

Created by: Strum355

Previously, ListDependencyRepos would return one result for every (package, version) tuple. In cases where we only want (package), we would be having potentially a large amount of unnecessary rows returned.

This PR allows for optionally excluding versions, returning only 1 row for every package name.

Closes https://github.com/sourcegraph/sourcegraph/issues/37691

Test plan

DB access covered by new unit test