Consolidate `bytes_view_hasher` and abstract_replication_strategy `factory_key_hasher` which are the same into a reusable utils::basic_xx_hasher.
To be used in a followup series for netw:msg_addr.
Closes#13530
* github.com:scylladb/scylladb:
utils: hashing: use simple_xx_hasher
utils: hashing: add simple_xx_hasher
utils: hashers: add HasherReturning concept
hashing: move static_assert to source file