[mlir][ods] Allow ArrayOfAttr implicit conversion to ArrayRef

mlir/include/mlir/IR/AttrTypeBase.td

class ArrayOfAttr<Dialect dialect, string attrName, string attrMnemonic,
   let extraClassDeclaration = [{
     auto begin() const { return getValue().begin(); }
     auto end() const { return getValue().end(); }
     bool empty() const { return getValue().empty(); }
     size_t size() const { return getValue().size(); }
     auto &front() const { return getValue().front(); }
     auto &back() const { return getValue().back(); }
     auto &operator[](size_t index) { return getValue()[index]; }
+    operator }] # returnType # [{() const { return getValue(); }
   }];
 }
 
 #endif // ATTRTYPEBASE_TD