[Proxy]: Adding support for exporting proxy Model

[abukhoy]

This feature adds support for exporting a proxy model, which disables the Embedding Layer and LM Head of a causal model.

Set enable_proxy = True to export the proxy model.
Set write_io = True to save input/output files during the generation stage.

Refer to the example script for implementation details.

Testing

Will update soon.

[vbaddi]

Thanks @abukhoy
Can we extend it to VLM also? Assuming Vision can have full model, the decoder_wrapper can have enable_proxy flag?