feat: Zero-copy deserialization

Currently, during deserialization, data is always copied from the deserializer when deserializing into a `Cow`, which always results in a `Cow::Owned`, thus copying the data.

There seem to be ways to mitigate this (e.g. using [`#[serde(borrow)]`](https://serde.rs/field-attrs.html#borrow) or introducing [`serde_with::BorrowCow`](https://docs.rs/serde_with/latest/serde_with/struct.BorrowCow.html)). When I tried this out briefly, I ended up sprinkling `borrow` all over the place, not sure, if this is actually required.

Also, adding validation to the deserialization through `try_from` seems to have complicated things to be less straightforward.

I'm sure there is some good way of doing this optimization.