Rollup merge of #52930 - eddyb:issue-52489, r=cramertj

rustc_resolve: record single-segment extern crate import resolutions.

Fixes #52489 by recording special-cased single-segment imports for later (e.g. stability) checks.

cc @alexcrichton @Mark-Simulacrum @petrochenkov

Does this need to be backported?

diff --cc src/librustc_resolve/resolve_imports.rs
Simple merge