C++ proposal: There are exactly 8 bits in a byte

I'm totally fine with enforcing that int8_t == char == 8-bits, however I'm not sure about spreading the misconception that a byte is 8-bits. A byte with 8-bits is called an octet.

At the same time, a `byte` is already an "alias" for `char` since C++17 anyway[1].

[1] https://en.cppreference.com/w/cpp/types/byte