Rollup merge of #94242 - compiler-errors:fat-uninhabitable-pointer, r=michaelwoerister

properly handle fat pointers to uninhabitable types

Calculate the pointee metadata size by using `tcx.struct_tail_erasing_lifetimes` instead of duplicating the logic in `fat_pointer_kind`. Open to alternatively suggestions on how to fix this.

Fixes #94149

r? ````@michaelwoerister```` since you touched this code last, I think!

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -449,7 +449,10 @@ fn pointer_or_reference_metadata<'ll, 'tcx>(
             // This is a thin pointer. Create a regular pointer type and give it the correct name.
             debug_assert_eq!(
                 (thin_pointer_size, thin_pointer_align),
-                cx.size_and_align_of(ptr_type)
+                cx.size_and_align_of(ptr_type),
+                "ptr_type={}, pointee_type={}",
+                ptr_type,
+                pointee_type,
             );
 
             unsafe {