Refactor IPEX CausalLM for better model architecture scale

[ofirzaf]

What does this PR do?

Use AutoModel mechanism to infer method implementation for different model architectures automatically. This will allow better scalability to different model architecture.

@echarlaix

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[HuggingFaceDocBuilderDev]

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