[CORE] Adding support for insertion of soft-tuned prompts

[SwapnilDreams100]

This PR adds support for inserting soft-tuned prompts into the input embeddings (trained using PEFT).

This functionality is required by the IBM team.

Summary of Changes:

• New prompt_adapter folder similar to the lora folder to create a LRU cache management system for multiple prompt adapters
• New prompt_adapter_config engine parameter - for easy extension to more sophisticated prompt-tuning techniques in the future
• New prompt_adapter_request parameter added to the generate functionality of the LLM_Engine
• Current support for several models like bloom, llama, mistral, easily extensible for others
• Simple test demonstrating that prompt adapters work for bloom
• Some parameter documentation still pending, will complete post successful code review

[Yard1]

Some high level comments - if this is not time sensitive, I think it would be good if we could come up with some more generic APIs to promote code reuse between LoRA and prompt adapter

[SwapnilDreams100]

Hey @Yard1,
I have addressed your comments on this soft prompt tuning PR. Some updates:

• New adapter_commons folder with all the common code between LoRA and Prompt Adapters abstracted
• Reduced redundancy of having to add the adapter addition code in all model classes by extending the VocalParallelEmbedding layer
• New parameter enable_prompt_adapter for more consistency w LoRA
• Added testing for multi-adapter inference

After your review, happy to add more extensive tests + docs.

[Yard1]

@SwapnilDreams100 thanks! let me take a look

[SwapnilDreams100]

Hi @Yard1 just a friendly reminder to review this PR when you get a chance, thanks!
Once this design is approved, happy to update this with support for prefix tuning as well, which should be similar in design!

[g-eoj]

Hi @SwapnilDreams100, I have an initial implementation of adapter support for the OpenAI entry points based on https://github.com/SwapnilDreams100/vllm/tree/main. Would you be open to me contributing to your PR?

[Yard1]

Approving pending CI passing

[g-eoj]

@SwapnilDreams100 first of all congrats!

I'd like to add tests for the openai server, would it be best to wait for this to merge so I can open my own PR against main?

[SwapnilDreams100]

Sounds good @g-eoj, big thank you for your help!

[SwapnilDreams100]

Hey @Yard1 are we good to merge?

[njhill]

Thanks for this epic effort @SwapnilDreams100!! And big thanks to @Yard1 for the many detailed reviews.

I'll merge it before any new conflicts pop up!

[SwapnilDreams100]

Big thank you to @Yard1 for your guidance on this, this was a great learning experience!