Add wav2vec2 support - export and audio tasks modeling

[JingyaHuang]

What does this PR do?

• Exporter support of wav2vec2

• tiny test

optimum-cli export neuron --model hf-internal-testing/tiny-random-Wav2Vec2Model --task audio-xvector --batch_size 1 --audio_sequence_length 74400 --auto_cast matmul --auto_cast_type bf16 tiny_wav2vec_neuron/

• regular model

optimum-cli export neuron --model facebook/wav2vec2-large-960h-lv60-self --task audio-xvector --batch_size 1 --audio_sequence_length 74400 --auto_cast matmul --auto_cast_type bf16 wav2vec_neuron/

• Neuron modeling for audio tasks
• Transformers pipeline support
• Tests
• Documentation

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]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[dacorvo]

Thank you for the pull-request, looks good to me !

[dacorvo]

Good ! We can still launch them manually