fix: resolve all inference vars in `InferenceResult::assoc_resolutions`
I think this fixes '#13773, ~but still haven't found repro. I'll try finding one so we can have a regression test~.
We should resolve every inference variable in `InferenceResult` after inference is done. We started recording `Substitution`s for each resolved associated items in #13725, but failed to do so which causes crash when analyzing source in IDE layer.
16de9a7130