Rollup merge of #159525 - folkertdev:stabilize-x86-i128-asm, r=Amanieu

Stabilize passing 128-bit integers via vector registers with `asm!` on x86

tracking issue: https://github.com/rust-lang/rust/issues/133416
reference PR: https://github.com/rust-lang/reference/pull/2313

# Stabilization report

## Summary

Stabilize passing 128-bit integers via vector registers with `asm!` on x86 and x86_64:

```rust
// Use 128-bit integers with vector registers.
let mut v = 0u128;

asm!("/* {:x} */", in(xmm_reg) v);
asm!("/* {:x} */", out(xmm_reg) v);

asm!("/* {:y} */", in(ymm_reg) v);
asm!("/* {:y} */", out(ymm_reg) v);

asm!("/* {:z} */", in(zmm_reg) v);
asm!("/* {:z} */", out(zmm_reg) v);
```

32-bit and 64-bit integer types can already be passed via vector registers. LLVM has supported 128-bit integers since 2019, see https://github.com/llvm/llvm-project/issues/42502, so `rustc` not supporting them seems like an oversight.

This feature is part of [`asm_experimental_reg`](https://github.com/rust-lang/rust/issues/133416). We're not stabilizing that feature as a whole, but only pull out part of it.

## History

- https://github.com/rust-lang/rust/pull/151059

## Open questions

None.

r? Amanieu