Stack and streaming conformer support (#141)

* added csrc/stack.cc

* stack: added checks

* added copyright info

* passed cpp style checks

* formatted code

* added some support for streaming conformer model support (not verified)

* code lint

* made more progress with streaming conformer support (not working yet)

* passed style check

* changes as suggested by @csukuangfj

* added some debug info

* fixed style check

* Use Cat to replace Stack

* remove debug statements

---------

Co-authored-by: Jingzhao Ou (jou2019) <jou2019@cisco.com>
Co-authored-by: Fangjun Kuang <csukuangfj@gmail.com>

sherpa-onnx/csrc/onnx-utils.h

@@ -75,6 +75,9 @@ void Print2D(Ort::Value *v);
 // Print a 3-D tensor to stderr
 void Print3D(Ort::Value *v);
 
+// Print a 4-D tensor to stderr
+void Print4D(Ort::Value *v);
+
 template <typename T = float>
 void Fill(Ort::Value *tensor, T value) {
   auto n = tensor->GetTypeInfo().GetTensorTypeAndShapeInfo().GetElementCount();