[TRT RTX EP] Fix bug for generating the correct subgraph in GetCapability (#26132)

### Description
In current TRT RTX EP/ TRT EP implementation, when constructing the
`IndexedSubGraph`, for some cases, it will include the node's unused
output as the SubGraph's output. So, it will return the incorrect
`IndexedSubGraph` from its GetCapability to ORT.
Add the logic to prevent adding the unused node's output.

With this fix, we can avoid generating the incorrect EPContext model
where the EPContext node has unused output.

Author: chilo-ms

onnxruntime/core/providers/nv_tensorrt_rtx/nv_execution_provider.cc

@@ -1466,12 +1466,15 @@ std::unique_ptr<IndexedSubGraph> NvExecutionProvider::GetSubGraph(SubGraph_t gra
           fused_inputs.erase(it);
           erased.insert(output);
         }
-        // Only when output is neither in input list nor erased list, add the output to output list
+        // Only when output is neither in input list nor erased list, and the output is consumed by another node, add the output to output list
         else if (erased.find(output) == erased.end()) {
           if (graph_output_names.find(output->Name()) != graph_output_names.end()) {
             graph_outputs_to_add[output] = output_order;
           }
-          fused_outputs[output] = output_order++;
+
+          if (graph.GetGraph().GetConsumerNodes(output->Name()).size() > 0) {
+            fused_outputs[output] = output_order++;
+          }
         }
       }
     }

onnxruntime/core/providers/tensorrt/tensorrt_execution_provider.cc

@@ -2114,12 +2114,15 @@ std::unique_ptr<IndexedSubGraph> TensorrtExecutionProvider::GetSubGraph(SubGraph
           fused_inputs.erase(it);
           erased.insert(output);
         }
-        // Only when output is neither in input list nor erased list, add the output to output list
+        // Only when output is neither in input list nor erased list, and the output is consumed by another node, add the output to output list
         else if (erased.find(output) == erased.end()) {
           if (graph_output_names.find(output->Name()) != graph_output_names.end()) {
             graph_outputs_to_add[output] = output_order;
           }
-          fused_outputs[output] = output_order++;
+
+          if (graph.GetGraph().GetConsumerNodes(output->Name()).size() > 0) {
+            fused_outputs[output] = output_order++;
+          }
         }
       }
     }