Hash faster by not using derive

[jrose-signal]

Uuid currently uses derive(Hash), but this calls through to an array's default implementation, which in turn calls to the implementation for slices, which includes a length prefix and goes element by element. Instead, it could just call state.write(&self.0) directly.

[KodrAus]

The Hash trait doesn’t guarantee stability of hashes unless you have control over both the hasher and type being hashed, so I think we should be able to make this change.

It’s technically unrelated, but what we can’t unfortunately do is change how we compute hashes in v1, v3, or v5 UUIDs, or else we’d start computing a different UUID for the same input.

[jrose-signal]

That's fine, those already pass the bytes directly. (And they are fully specified by the UUID standard, so they're either correct or wrong as they are.)