[mlir] Reorder shape assuming bufferization.

[tpopp]

Summary

The previous ordering continued to use the original assuming after
replacing it which is not allowed. Now, inline the region from the old
into the new before the replacement.

[jpienaar]

Did one of sanitizers flag this?

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

matchAndRewrite(AssumingOp op, ArrayRef<Value> operands,
     for (auto result : op.getResults()) {
       auto originalType = result.getType();
       Type convertedType = getTypeConverter()->convertType(originalType);
       newResultTypes.push_back(convertedType);
     }
 
     auto newAssumingOp =
         rewriter.create<AssumingOp>(op.getLoc(), newResultTypes, op.witness());
-
-    rewriter.replaceOp(op, newAssumingOp.getResults());
     rewriter.inlineRegionBefore(op.doRegion(), newAssumingOp.doRegion(),
                                 newAssumingOp.doRegion().end());
+    rewriter.replaceOp(op, newAssumingOp.getResults());
 
     return success();
   }
 };
 } // namespace
 
 namespace {
 class ConvertAssumingYieldOpTypes