Auto merge of #133990 - Walnut356:static_const, r=workingjubilee

[Debuginfo] Force enum `DISCR_*` to `static const u64` to allow for inspection via LLDB

see [here](https://rust-lang.zulipchat.com/#narrow/channel/317568-t-compiler.2Fwg-debugging/topic/Revamping.20Debuginfo/near/486614878) for more info.

This change mainly helps `*-msvc` debugged with LLDB. Currently, LLDB cannot inspect `static` struct fields, so the intended visualization for enums is only borderline functional, and niche enums with ranges of discriminant cannot be determined at all .

LLDB *can* inspect `static const` values (though for whatever reason, non-enum/non-u64 consts don't work).

This change adds the `LLVMRustDIBuilderCreateQualifiedType` to the rust FFI layer to wrap the discr type with a `const` modifier, as well as forcing all generated integer enum `DISCR_*` values to be u64's. Those values will only ever be used by debugger visualizers anyway, so it shouldn't be a huge deal, but I left a fixme comment for it just in case.. The `tag` also still properly reflects the discriminant type, so no information is lost.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2008,6 +2008,12 @@ unsafe extern "C" {
         AlignInBits: u32,
     ) -> &'a DIDerivedType;
 
+    pub fn LLVMRustDIBuilderCreateQualifiedType<'a>(
+        Builder: &DIBuilder<'a>,
+        Tag: c_uint,
+        Type: &'a DIType,
+    ) -> &'a DIDerivedType;
+
     pub fn LLVMRustDIBuilderCreateLexicalBlock<'a>(
         Builder: &DIBuilder<'a>,
         Scope: &'a DIScope,