Improve hash_function used by TreeEnsemble (#22043)

### Description
unordered_map are implemented in a different way on VisualStudio and
gcc. It seems that inserting consecutive keys has a poor performance on
Windows.



### Motivation and Context
Improve the performance of onnxruntime when initializing trees.

onnxruntime/core/providers/cpu/ml/tree_ensemble_aggregator.h

@@ -23,7 +23,9 @@ struct TreeNodeElementId {
   }
   struct hash_fn {
     std::size_t operator()(const TreeNodeElementId& key) const {
-      return static_cast<std::size_t>(static_cast<uint64_t>(key.tree_id) << 32 | static_cast<uint64_t>(key.node_id));
+      // unordered_map has poor performance on Windows when inserting consecutive keys.
+      // keys are usually inserted with key.node_id being incremented at each iteration.
+      return static_cast<std::size_t>(static_cast<uint64_t>(key.tree_id) | static_cast<uint64_t>(key.node_id) << 32);
     }
   };
 };