feat: add python binding for rust llm modules

[biswapanda]

What does the PR do?

TODO:

• Add readme.md docs to run the examples
• vllm_backed clean up

Adds python binding for llm modules:

• model deployment card
• preprocessor
• backend
• http service

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• build
• ci
• docs
• feat
• fix
• perf
• refactor
• revert
• style
• test

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Background

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• closes GitHub issue: add python binding for preprocessor and backend #257

[grahamking]

I don't think you need all of this.

In tio I do:

            let frontend = ServiceFrontend::<
                SingleIn<ChatCompletionRequest>,
                ManyOut<Annotated<ChatCompletionResponseDelta>>,
            >::new();

and it is equivalent. I think that's the new way.

Take a look at launch/tio/src/input/text.rs for example.