[CIR][CodeGen] handle zero init padding case (#1257)

I continue to use `csmith` and catch run time bags. Now it's time to fix
the layout for the const structs.

There is a divergence between const structs generated by CIR and the
original codegen. And this PR makes one more step to eliminate it. There
are cases where the extra padding is required - and here is a fix for
some of them. I did not write extra tests, since the fixes in the
existing already covers the code I added. The point is that now the
layout for all of these structs in the LLVM IR with and without CIR is
the same.

clang/lib/CIR/CodeGen/CIRGenExprConst.cpp

@@ -660,11 +660,6 @@ bool ConstStructBuilder::Build(InitListExpr *ILE, bool AllowOverwrite) {
       continue;
     }
 
-    if (ZeroInitPadding &&
-        !DoZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite, SizeSoFar,
-                           ZeroFieldSize))
-      return false;
-
     if (ZeroInitPadding &&
         !ApplyZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite,
                               SizeSoFar, ZeroFieldSize))