Better handle CRLF normalization

[jaybosamiya]

If we format a properly-formatted file that has Windows newlines, then verusfmt replaces them with Unix newlines (at least on a Unix system (possibly most confusingly with WSL?)); however, this may cause confusion on verusfmt --check since literally every line will look visually identical in the diff. It would be nice if we can detect this as the reason, and provide a better error message rather than dump the whole file in the -/+ of the diff.

Core issue hit originally by @jaylorch, likely due to git's handling of newline changes.