Integrate the functionality of serde_bytes into serde_as

[jonasbb]

serde_bytes provides a performance optimization for de-/serializing byte sequences. However, it does not have the same flexibility as serde_as. This crate could provide a Bytes type and implement the optimized behavior for it.

It should be compatible with all types supported by serde_bytes, like &[u8], Box<[u8]>, Vec<u8>, Cow<'_, [u8]>.
The support for Option<T> should then come from serde_as.

[jonasbb]

The feature is implemented as the Bytes type in version 1.7.0.