Auto merge of #107224 - nikic:llvm-16, r=cuviper

Upgrade to LLVM 16

This updates Rust to LLVM 16. It also updates our host compiler for dist-x86_64-linux to LLVM 16. The reason for that is that Bolt from LLVM 15 is not capable of compiling LLVM 16 (llvm/llvm-project#61114).

LLVM 16.0.0 has been [released](https://discourse.llvm.org/t/llvm-16-0-0-release/69326) on March 18, while Rust 1.70 will become stable on June 1.

Tested images: `dist-x86_64-linux`, `dist-riscv64-linux` (alt), `dist-x86_64-illumos`, `dist-various-1`, `dist-various-2`, `dist-powerpc-linux`, `wasm32`, `armhf-gnu`
Tested images until the usual IPv6 failures: `test-various`

Author: bors