Auto merge of #56198 - bjorn3:cg_ssa_refactor, r=eddyb

Refactor rustc_codegen_ssa

cc #56108 (not all things are done yet)

This removes an unsafe method from cg_ssa.

r? @eddyb
cc @sunfishcode

src/librustc_codegen_utils/lib.rs

@@ -60,5 +60,3 @@ pub fn check_for_rustc_errors_attr(tcx: TyCtxt) {
         }
     }
 }
-
-__build_diagnostic_array! { librustc_codegen_utils, DIAGNOSTICS }