- Convert panics to diagnostics with id `Panic`, severity `Fatal`, and
the error as the diagnostic message, annotated with a `Span` with empty
code block and no range.
- Updates the post-linting message diagnostic handling to track the
maximum severity seen, and then prints the "report a bug in ruff"
message only if the max severity was `Fatal`
This depends on the sorting changes since it creates diagnostics with no
range specified.