[V0 Deprecation] Remove pooling model support in V0

[maxdebayser]

Continuation of PR #23302

Summary

• drop pooling model runner and related code paths in V0 worker
• simplify V0 engine to handle only sampling requests
• add stubs that raise for pooling model entry points

@DarkLight1337 , @noooop , do you remember anything else to remove?

[gemini-code-assist]

Code Review

This pull request effectively removes support for pooling models in the vLLM V0 worker, which aligns with the stated objective. The changes are comprehensive, touching upon the engine, worker, sequence management, and tests to eliminate the V0 pooling code paths. Key modifications include the removal of PoolingModelRunner and V0-specific pooling metadata, updating LLMEngine and AsyncLLMEngine to handle only sampling requests, and stubbing out pooling-related entry points to raise NotImplementedError. The removal of token_type_ids and related logic is also consistent with this goal. The code modifications appear to be correct and consistently applied across the repository. I have not found any issues of high or critical severity.

[DarkLight1337]

Not that I'm aware of.

[noooop]

I think it’s quite difficult to clean it up all at once. It might take some time to completely remove all the “compatibility code”.

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I hope this PR landing as soon as possible, so we can focus our optimization efforts on a single engine.

[maxdebayser]

I'm running into weird typing issues. Why is EngineClient.generate() not async if in classes that implement this interface the method is async (see AssyncLLMEngine and AssyncLLM ) . And why is it called without await?

[DarkLight1337]

cc @robertgshaw2-redhat

[noooop]

@maxdebayser

Remove all run_with_both_engines in vllm/tests/models/language/pooling and vllm/tests/entrypoints/

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Let's land this PR quickly, as long as ci turns green, then polish it in subsequent PRs.

[noooop]

clean up v0_only in tests/models/registry.py

[maxdebayser]

@DarkLight1337 , the basic tests are passing now. Can you enable the full test suite?

[DarkLight1337]

Can merge if tests pass

[noooop]

@DarkLight1337

Is the failed test caused by a flaky test?

[DarkLight1337]

Yes

[maxdebayser]

Follow-up issue: #23883