[clang] [CIR] Upstream support for FlattenCFG switch and SwitchFlatOp (PR #139154)

[Andy Kaylor via cfe-commits]

================
@@ -971,6 +971,52 @@ def SwitchOp : CIR_Op<"switch",
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// SwitchFlatOp
+//===----------------------------------------------------------------------===//
+
+def SwitchFlatOp : CIR_Op<"switch.flat", [AttrSizedOperandSegments,
+                                          Terminator]> {
+
+  let description = [{
+    The `cir.switch.flat` operation is a region-less and simplified
+    version of the `cir.switch`.
+    It's representation is closer to LLVM IR dialect
----------------
andykaylor wrote:

```suggestion
    Its representation is closer to LLVM IR dialect
```

Also, the formatting is odd here. Can you clean up the word wrap locations?

https://github.com/llvm/llvm-project/pull/139154