Rollup merge of #127015 - Urgau:non_local_def-tmp-allow, r=lqd

Switch back `non_local_definitions` lint to allow-by-default

This PR switch back (again) the `non_local_definitions` lint to allow-by-default as T-lang is requesting some (major) changes in the lint inner workings in rust-lang/rust#126768 (comment).

This PR will need to be beta-backported, as the lint is currently warn-by-default in beta.