Auto merge of #48309 - mark-i-m:anon_param_lint, r=nikomatsakis

Auto merge of #48309 - mark-i-m:anon_param_lint, r=nikomatsakis

Make anon params lint warn-by-default

This is intended as a followup on anonymous parameters deprecation.

Cross-posting from #41686:

> After having read a bit more of the discussion that I can find, I propose a more aggressive deprecation strategy:
> - We make the lint warn-by-default as soon as possible
> - We make anon parameters a hard error at the epoch boundary

cc @matklad @est31 @aturon