8692: Fix panic caused by new Try trait definition r=flodiebold a=flodiebold
The new Try trait definition caused a query cycle for us. This adds recovery for that cycle, but also fixes the cause, which is that we went through the supertraits when resolving `<T as Trait>::Assoc`, which isn't actually necessary. I also rewrote `all_super_trait_refs` to an iterator before I realized what the actual problem was, so I kept that.
Fixes#8686.
Co-authored-by: Florian Diebold <flodiebold@gmail.com>
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