* Implement SourceUnitEnumChunker for GitLab
* Add GitLab engine integration test
* Use a SliceReporter instead of checking for nil reporters
* Use more generic VisitorReporter
* Merge logic from getReposFromGitlab into getAllProjectRepos
* Update integration test to have a lower bound
Unfortunately, the GitLab integration test does not appear to be
deterministic. Sometimes 36390 chunks are found, sometimes 36312, or
even lower.