Add Support for Frequency Penalties in On Device Sampling

[quic-sanising]

✨ Add Frequency Penalty Support to On Device Sampling

This PR adds support for the frequency_penalty parameter in On Device Sampling for QEffForCausalLM models. This parameter adjusts token selection based on how often tokens have already appeared in the generated output:

• Positive values discourage repetition and promote diversity.
• Negative values encourage repetition.
• Zero disables the penalty.

The implementation tracks token frequencies directly on the QAIC device using optimized scratch buffers, ensuring minimal overhead and maintaining high throughput. This feature integrates seamlessly with the existing include_sampler=True workflow and complements other supported strategies like repetition and presence penalties.

[quic-sanising]

Depends on PR #463.