Use sequences to create initial feeds for decoder subgraph (#13719)
Use sequences to create initial feeds for decoder subgraph instead of
beam_next_tokens
### Description
For TuLG models exporting of decoder is different from bart model.
Passing beam_next_tokens to the decoder while ort inferencing generated
incorrect result from pytorch inference.
This change will use sequences as inputs for the first iteration as well
### Motivation and Context
Pytorch and ORT inference for TuLG models was incorrect, keeping pytorch
as correct result we modified ort to match the result.