[clang] [CIR] Upstream StackSave and StackRestoreOp (PR #136426)

[Andy Kaylor via cfe-commits]

================
@@ -1419,6 +1419,50 @@ def CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
     }]>];
 }
 
+//===----------------------------------------------------------------------===//
+// StackSave & StackRestoreOp
----------------
andykaylor wrote:

```suggestion
// StackSaveOp & StackRestoreOp
```
For consistency, though I'm not sure why there are combined.

https://github.com/llvm/llvm-project/pull/136426