Don't record adjustments twice in `note_source_of_type_mismatch_constraint`
We call `lookup_method` a few times in `note_source_of_type_mismatch_constraint`, but that function has side-effects to the typeck results. Replace it with a less side-effect-y variant of the function for use in diagnostics.
Specifically the ICE in #112532 happens because we're recording deref adjustments twice for a call receiver, which causes `ExprUseVisitor` to be angry.
Fixes#112532
90e51f110c