Tie-break requirements with package name

This makes the ordering deterministic to improve debugging and user
experience.

src/pip/_internal/resolution/resolvelib/provider.py

@@ -57,7 +57,8 @@ def get_preference(
     ):
         # type: (...) -> Any
         transitive = all(parent is not None for _, parent in information)
-        return (transitive, bool(candidates))
+        key = next(iter(candidates)).name if candidates else ""
+        return (transitive, key)
 
     def find_matches(self, requirements):
         # type: (Sequence[Requirement]) -> Iterable[Candidate]