Sort error summary output by count then name

[anushamukka-dev]

Summary:
The error summary printed by print_error_summary ordered files and per-file error kinds by count alone, leaving ties in a nondeterministic map-iteration order. This made the output unstable and harder to read across runs.

Add a secondary sort key so entries with equal counts break ties by name: per-file error kinds tie-break on ErrorKind::to_name, and files tie-break on the path's display string. This makes the summary deterministic and human-readable.

Because ModulePath does not implement Ord, the file-level tie-break compares display strings, which requires a Display bound on the generic collect_and_sort helper (its sole caller passes ModulePath, which is Display). The stale TODO requesting this behavior is removed.

Differential Revision: D111620758

[meta-codesync]

@anushamukka-dev has exported this pull request. If you are a Meta employee, you can view the originating Diff in D111620758.

[NathanTempest]

Thanks for the cleanup. Making the summary deterministic by tie-breaking on name (count desc → name asc) is exactly right, and it resolves the stale TODO it removes. Bonus points for sort_by_cached_key caching the total + path string instead of recomputing per comparison, and Reverse reads much cleaner than the old negation.

One optional follow-up: since this changes ordering behavior, a small unit test on collect_and_sort asserting the count-desc / name-asc tie-break would lock it in (print_error_summary is stderr-only, but the helper returns a Vec, so it's easily testable via a #[cfg(test)] module). Not a blocker but happy to add it on our end. LGTM otherwise.

[meta-codesync]

This pull request has been merged in e6808ea.