Rollup merge of #113534 - oli-obk:simd_shuffle_dehackify, r=workingjubilee

Forbid old-style `simd_shuffleN` intrinsics

Don't merge before https://github.com/rust-lang/packed_simd/pull/350 has made its way to crates.io

We used to support specifying the lane length of simd_shuffle ops by attaching the lane length to the name of the intrinsic (like `simd_shuffle16`). After this PR, you cannot do that anymore, and need to instead either rely on inference of the `idx` argument type or specify it as `simd_shuffle::<_, [u32; 16], _>`.

r? `@workingjubilee`

compiler/rustc_error_codes/src/error_codes/E0439.md

@@ -16,7 +16,7 @@ extern "platform-intrinsic" {
 The `simd_shuffle` function needs the length of the array passed as
 last parameter in its name. Example:
 
-```
+```ignore (no longer compiles)
 #![feature(platform_intrinsics)]
 
 extern "platform-intrinsic" {