[llvm] [mlir] [MLIR] Add `InParallelOpInterface` for parallel combining operations (PR #157736)

[Han-Chung Wang via llvm-commits]

================
@@ -3935,6 +3934,20 @@ llvm::SmallBitVector ParallelInsertSliceOp::getDroppedDims() {
   return ::getDroppedDims(getSourceType().getShape(), getMixedSizes());
 }
 
+// ParallelCombiningOpInterface implementation
----------------
hanhanW wrote:

```suggestion
// ParallelCombiningOpInterface implementation.
```

https://github.com/llvm/llvm-project/pull/157736