Rollup merge of #119195 - asquared31415:named_asm_labels_fix, r=Amanieu

Make named_asm_labels lint not trigger on unicode and trigger on format args

Someone showed me some cursed code that used format args to create named labels, and rustc wasn't linting on that.  Additionally while fixing that, I noticed that Unicode alphabetic characters were being used as part of labels, when they are not actually permitted in labels.

r? ```@Amanieu```

Author: matthiaskrgr