[gcdebug] ignore _NeedAuthAccessMock instances When looping over gc.get_objects(), we'd crash in _NeedAuthAccessMock.__getattribute__.

[views] Fix 'gc' view to use 'repo_gc_stats' service

[services] Fix 'repo_gc_stats' to return a list of unreachable objects' repr

[services] Prevent 'repo_stats' service from aggregating information It's up to the consumer of the service to decide whether it wants aggregated data or not... Ensure the /siteinfo page rendering is not modified.