Fix LLM tests

[pablomlago]

Reason for this PR

See #1076.

Changes Made in this PR

Since transformers 4.46.0 (https://github.com/huggingface/transformers/releases/tag/v4.46.0), OPT attention mechanism relies, by default, on OPTSdpaAttention, thus resulting in the method replace_mha_with_quantizable_layers (https://github.com/pablomlago/brevitas/blob/master/src/brevitas_examples/llm/llm_quant/prepare_for_quantize.py#L11) not injecting the Brevitas layers.

Additionally, the signature of the forward function in OPTAttention was updated in transformers 4.46.0, thus requiring to update the signature of QuantMultiHeadAttention analogously, even if this attribute is not actually used.

Testing Summary

TODO

Risk Highlight

• This PR includes code from another work (please detail).
• This PR contains API-breaking changes.
• This PR depends on work in another PR (please provide links/details).
• This PR introduces new dependencies (please detail).
• There are coverage gaps not covered by tests.
• Documentation updates required in subsequent PR.

Checklist

• Code comments added to any hard-to-understand areas, if applicable.
• Changes generate no new warnings.
• Updated any relevant tests, if applicable.
• No conflicts with destination dev branch.
• I reviewed my own code changes.
• Initial CI/CD passing.
• 1+ reviews given, and any review issues addressed and approved.
• Post-review full CI/CD passing.

[nickfraser]

Open question about new pattern for layer replacement.

[nickfraser]

I think only @Giuseppe5's comment needs to be addressed, otherwise this can be merged IMO.

[Giuseppe5]

There's a bunch of test failing on the extended test suite @pablomlago