Auto merge of #22838 - petrochenkov:bytelit, r=alexcrichton

This patch changes the type of byte string literals from `&[u8]` to `&[u8; N]`.
It also implements some necessary traits (`IntoBytes`, `Seek`, `Read`, `BufRead`) for fixed-size arrays (also related to #21725) and adds test for #17233, which seems to be resolved.

Fixes #18465
[breaking-change]

diff --cc src/librustc_trans/trans/_match.rs
Simple merge

diff --cc src/librustc_trans/trans/consts.rs
Simple merge

diff --cc src/librustc_typeck/check/mod.rs
Simple merge