Auto merge of #82864 - jyn514:short-circuit, r=GuillaumeGomez

rustdoc: Don't enter an infer_ctxt in get_blanket_impls for impls that aren't blanket impls

Less broken version of https://github.com/rust-lang/rust/pull/82856.

get_blanket_impls is a *very* hot region of rustdoc, so even small changes like this should help. Unfortunately I don't have benchmarks for this until https://github.com/rust-lang/rustc-perf/pull/802 is merged.

diff --cc src/librustdoc/clean/blanket_impl.rs
Simple merge