This is a set of a few cosmetic changes in dht/token. Mostly some comments and a simplification of `midpoint()`.
Closes#8803
* github.com:scylladb/scylla:
dht: token: add a comment excusing the `const bytes&` constructor
dht: token: simplify midpoint()
dht: token: add a comment to normalize()
dht: token: use {read,write}_unaligned instead of std::copy_n
dht: token-sharding: fix a typo in a comment
0048c404d2