Rollup merge of #131686 - Urgau:fast-path-vis, r=lqd

Add fast-path when computing the default visibility

This PR adds (or more correctly re-adds the) fast-path when computing the default visibility, by taking advantage of the fact that the "interposable" requested visibility always return the "default" codegen visibility.

Should address the small regression observed in rust-lang/rust#131111 (comment).

r? `@lqd`