I want to get the“hidden_states” data in the Bert model

### Describe the feature request

I'm running a TTS project where the Bert model needs to get the“hidden_states” component of the middle layer output for later processing. I'm using C + + and can't seem to find a way to get the middle layer output, any suggestions?

### Describe scenario use case

This method is handy for using the Bert Model, because hidden_states are also useful features, which can be implemented in the Python version of Transformer, but is difficult to implement in C + + .

Start by reviewing ONNX Runtime's C++ inference APIs and the BERT model path to determine how intermediate hidden-state outputs are represented. Compare this with the Python Transformer behavior described in the issue. Done means the supported approach for retrieving middle-layer hidden states in C++ is clearly defined and covered by appropriate validation.

Written by the indexing model from the issue text.