[onnxruntime_perf_test] Fix custom_allocator_ destruction order. (microsoft#24136)

Move the allocator data member declaration before the `Ort::Value`
container data members that might use the allocator so that the
`Ort::Value` containers will be destroyed first.

`custom_allocator_` may be used as the allocator for the `Ort::Value`s
in `test_inputs_` and `outputs_`. The allocator shouldn't be destroyed
before `Ort::Value`s allocated with it are freed.

Author: edgchen1

onnxruntime/test/perftest/ort_test_session.h

@@ -37,9 +37,10 @@ class OnnxRuntimeTestSession : public TestSession {
   Ort::Session session_{nullptr};
   std::mt19937 rand_engine_;
   std::uniform_int_distribution<int> dist_;
-  std::vector<std::vector<Ort::Value>> test_inputs_;
   OrtAllocator* allocator_ = Ort::AllocatorWithDefaultOptions();
+  // Note: custom_allocator_, if used, must outlive the `Ort::Value`s allocated with it in test_inputs_ and outputs_.
   Ort::Allocator custom_allocator_{nullptr};
+  std::vector<std::vector<Ort::Value>> test_inputs_;
   std::vector<Ort::Value> outputs_;
   std::vector<std::string> output_names_;
   // The same size with output_names_.