Extend Pad Fusion for AveragePool (#21556)

### Description
This extends the existing pad_fusion for AveragePool operator i.e. fuse
Pad if it is followed by AveragePool operator.



### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->

onnxruntime/core/optimizer/pad_fusion.cc

@@ -12,7 +12,7 @@ namespace onnxruntime {
  * It matches following pattern:
  *     Pad
  *      |
- *   Conv/MaxPool
+ *   Conv/MaxPool/AveragePool
  */
 bool PadFusion::SatisfyCondition(const Graph& graph, const Node& node, const logging::Logger&) const {
   // if Pad has input axis, don't fuse it.
@@ -28,6 +28,7 @@ bool PadFusion::SatisfyCondition(const Graph& graph, const Node& node, const log
 
   const Node& child_node = *node.OutputNodesBegin();
   if (!graph_utils::IsSupportedOptypeVersionAndDomain(child_node, "Conv", {1, 11}) &&
+      !graph_utils::IsSupportedOptypeVersionAndDomain(child_node, "AveragePool", {1, 7, 10, 11, 19}) &&
       !graph_utils::IsSupportedOptypeVersionAndDomain(child_node, "MaxPool", {1, 8, 10, 11, 12})) {
     return false;
   }

onnxruntime/core/optimizer/pad_fusion.h

@@ -8,7 +8,7 @@
 namespace onnxruntime {
 /*
  *   This fusion submerges a Pad operator to it's child
- *   Conv or MaxPool operator, if and only if PadFusion::SatisfyCondition()
+ *   Conv or MaxPool or AveragePool operator, if and only if PadFusion::SatisfyCondition()
  *   is true.
  */
 class PadFusion : public RewriteRule {