refactor: replace Chunks with BytesMut

[thomaseizinger]

The entire Chunks module looks similar to what Bytes and BytesMut do so we can probably throw that away and use the bytes crate instead.

Is likely more efficient although that is not my main concern. We just want to maintain as little code as possible.

[mxinden]

Note that we went the opposite way in the past: #77

(Not opposing the idea proposed here. Might help us to make a more informed decision.)

[thomaseizinger]

Interesting, I'll have to dig into that.