[RFC]: Drop Support for OpenVINO

[simon-mo]

Motivation.

OpenVINO backend was initially integrated as an alternatively to the CPU backend and has branched out the vLLM execution logic for every levels (executor, model runner, and attention backend). #5377

Over the last 9 months, we have been the following

• Relatively low usage as reported in Github Issues and Slack discussions
• The Intel CPU codepath is more mature and largely compatible for Arm as well.
• The OpenVINO code path complicated with codebase
• CI and build became difficult to maintain

I would like to propose to move OpenVINO off from the main codebase, and transition to a vLLM out of tree platform plugin if desired. OpenVINO can follow the same approach as Ascend and Spyre with the plugin approach #11162

Proposed Change.

• Remove OpenVINO codepath, build and test.
• Optionally, create vllm-project/vllm-openvino if the developers want to maintain plugin level compatibility.

Feedback Period.

2 weeks. By March 20.

CC List.

cc @ilya-lavrenov @WoosukKwon @youkaichao @robertgshaw2-redhat @mgoin

Any Other Things.

No response

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[youkaichao]

agree that a plugin might be better for openvino, similar to https://github.com/vllm-project/vllm-spyre and https://github.com/vllm-project/vllm-ascend

[simon-mo]

https://github.com/vllm-project/vllm-openvino has been created. We will move forward with the removal.

[russellb]

I will post a PR to do the removal from main.

[russellb]

#15339