Rollup merge of #60169 - varkor:tidy-unnecessary-ignore-newline, r=kennytm

Warn when ignore-tidy-linelength is present, but no lines are too long

It's easy for a `// ignore-tidy-linelength` to be added when there is a genuine need to ignore a file's line length, but then after refactoring the need is gone, but the tidy directive is not removed. This means that in the future, further editing may accidentally add unnecessarily long lines. This change forces `// ignore-tidy-linelength` to be used exactly when necessary, to make sure such changes are intentional.