auto merge of #18440 : japaric/rust/hash, r=alexcrichton
- The signature of the `*_equiv` methods of `HashMap` and similar structures have changed, and now require one less level of indirection. Change your code from:
- The generic parameter `T` of the `Hasher::hash<T>` method have become `Sized?`. Downstream code must add `Sized?` to that method in their implementations. For example: