Suggest {to,from}_ne_bytes for transmutations between arrays and integers, etc

[bend-n]

implements #136067

Rust has helper methods for many kinds of safe transmutes, for example integer<->bytes. This is a lint against using transmute for these cases.

fn bytes_at_home(x: [u8; 4]) -> u32 {
   transmute(x)
}

// other examples
transmute::<[u8; 2], u16>();
transmute::<[u8; 8], f64>();
transmute::<u32, [u8; 4]>();
transmute::<char, u32>();
transmute::<u32, char>();

It would be handy to suggest u32::from_ne_bytes(x).
This is implemented for [u8; _] -> {float int}

This also implements the cases:
fXX <-> uXX = {from_bits, to_bits}
uXX -> iXX via cast_unsigned and cast_signed
{char -> u32, bool -> n8} via from
u32 -> char via from_u32_unchecked (note: notes from_u32().unwrap()) (contested)
u8 -> bool via == (debatable)

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try-job: aarch64-gnu
try-job: test-various