Add feature to use `AlignedVec` over `Vec` for eventual consistency API.

[ChillFish8]

Currently, we use unaligned Vec<u8> buffers for Documents, while this is fine... We would be better off using the AlignedVec as it allows for greater usage with rkyv and it's zero-copy system.

[ChillFish8]

After some discussion, this actually might require a slightly smarter design, since doing this in a naive way would force another allocation when realistically we can actually remove an allocation using a DataView.