Use std::byte for bytes_type

[jwakely]

For v2 (or when merging into the IS) we should consider using std::byte instead of unsigned char.

[isnullxbh]

Hello, Mr. Wakely!

Quote from en.cppreference.com:

Like char and unsigned char, it can be used to access raw memory occupied by other objects (object representation), but unlike those types, it is not a character type and is not an arithmetic type. A byte is only a collection of bits, and the only operators defined for it are the bitwise ones.

What is the advantage of usage of std::byte instead unsigned char type? Should we use type that was invented in the first place to hold a raw byte in memory without the assumption that it's a character?