Zerocopy RsVec

[somethingelseentirely]

This adds a zerocopy capabilities based on the anybytes crate.

[Cydhra]

That could probably use a forced rebase

[somethingelseentirely]

Sorry, completely forgot to clean it up after all the other changes happened 🙇‍♂️ 😅
(The failing tests in the CI are because of the serde/zerocopy incompability.)

[Cydhra]

No, PackedSlice doesn't implement Index and has no len() method, thats why the tests fail

[somethingelseentirely]

I think that's a follow-up error, unless I'm missing something.
PackedSlice implements

impl<T> AsRef<[T]> for PackedSlice<T>
where
    T: FromBytes,

but with the serde feature enabled, FromBytes and AsBytes don't get derived, so the blanket implementation won't exist, so it doesn't have Index or len().