10456: fix: Avoid cycle when lowering predicates for associated item lookup r=flodiebold a=jonas-schievink
Fixes https://github.com/rust-analyzer/rust-analyzer/issues/10386
(the salsa bug persists, but this lets us avoid it by fixing the underlying bug)
This reimplements the rustc logic in b27661eb33/compiler/rustc_typeck/src/collect.rs (L556): When resolving an associated type `T::Item`, we've previously lowered all predicates that could affect `T`, but we actually have to look only at those predicates whose traits define an associated type of the right name.
Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>
5bdae82947