[mlir] Use PatternRewriter infrastructure for shape.assuming bufferization

[tpopp]

Summary

Without this, legalization might not recursively handle child ops properly.
Additionally, this is required for pattern rewriting to properly rollback conversions.

[herhut]

Thanks for fixing this!

mlir/lib/Dialect/Shape/Transforms/ShapeTypeConversion.cpp

for (auto result : assumingOp.getResults()) {
       auto originalType = result.getType();
       Type convertedType = converter->convertType(originalType);
       newResultTypes.push_back(convertedType);
     }
 
     auto newAssumingOp = rewriter.create<shape::AssumingOp>(
         assumingOp.getLoc(), newResultTypes, assumingOp.witness());
 
-    // Handle the region transfer carefully here to avoid assertions that both
-    // operations are valid at replacement time.
-    newAssumingOp.doRegion().push_back(new Block());
     rewriter.replaceOp(assumingOp, newAssumingOp.getResults());
-    newAssumingOp.doRegion().takeBody(assumingOp.doRegion());
+    rewriter.inlineRegionBefore(assumingOp.doRegion(), newAssumingOp.doRegion(),
+                                newAssumingOp.doRegion().end());
 
     return success();
   }
 };
 
 struct ShapeTensorToMemrefPass
     : public ShapeTensorToMemrefBase<ShapeTensorToMemrefPass> {
   void runOnFunction() override {