Auto merge of #115893 - RalfJung:match-require-partial-eq, r=oli-obk

lint towards rejecting consts in patterns that do not implement PartialEq

I think we definitely don't want to allow such consts, so even while the general plan around structural matching is up in the air, we can start the process of getting non-PartialEq matches out of the ecosystem.

Author: bors