Rollup merge of #136326 - Zalathar:llvm-di-builder-ref, r=nikic

Replace our `LLVMRustDIBuilderRef` with LLVM-C's `LLVMDIBuilderRef`

Inspired by trying to split #134009 into smaller steps that are easier to review individually.

This makes it possible to start incrementally replacing our debuginfo bindings with the ones in the LLVM-C API, all of which operate on `LLVMDIBuilderRef`.

There should be no change to compiler behaviour.

Author: matthiaskrgr