[Core] Enable HF processing on GPU

[DarkLight1337]

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Purpose

This PR completes the basic features of #21995 with documentation and tests for it.

• Support GPU processor outputs and cast them back to CPU for serialization
• Update profiling code to run a full batch through the processor when GPU processing is enabled
• Add optimization docs for multi-modal processing

Test Plan

Added entrypoints tests to test the functionality.

Test Result

(Optional) Documentation Update

[gemini-code-assist]

Code Review

This pull request enables Hugging Face processor execution on the GPU, a valuable performance enhancement. The changes include comprehensive documentation updates, new tests to validate the functionality, and significant refactoring to support the new feature.

The core logic for GPU processing, including moving data to and from the device and handling configuration, appears correct. The refactoring in the worker and test files improves code clarity and maintainability.

I've identified a couple of high-severity issues related to inefficient dummy data generation during profiling runs in both the GPU and TPU model runners. These inefficiencies could impact the accuracy of memory profiling and should be addressed. My review includes specific suggestions to resolve these issues.

[mergify]

Documentation preview: https://vllm--22070.org.readthedocs.build/en/22070/

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @DarkLight1337.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork