Hash consistency for Borrow + Hash traits for Utf8Bytes

[yhx-12243]

As mentioned in documentation of rust standard library, if a type implements both Borrow and Hash, they should be consistent: hash(x) == hash(x.borrow()), (cf. https://rust-lang.github.io/rust-clippy/master/index.html#impl_hash_borrow_with_str_and_bytes)

However, the current implementation is not consistent. It may cause unexpected behaviors when using HashMap for these.

[daniel-abramov]

Good catch, thanks!

(cf. https://rust-lang.github.io/rust-clippy/master/index.html#impl_hash_borrow_with_str_and_bytes)

NB: Note that the particular lint covers a similar, but different case.

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@sdroege, mentioning you just in case you rely on the current Hash implementation somewhere in other crates 🙂

[sdroege]

I don't, thanks for catching this :)