Enable Pipeline Parallelism on torchax path

[Chenyaaang]

Description

The implementation for Pipeline Parallelism are splitted into the following small PRs.

• Util functions for PP on Jax (Create Utils functions for PP #1042)
• worker changes (Enable Pipeline Parallelism on jax worker #1043)
• runner changes (Enable Pipeline Parallelism on Jax runner #1053)
• platform changes (Enable Pipeline Parallelism on Jax TPU platform #1054)
• torchax changes (The current PR)
• Jax changes
• Single host changes (this will be in vLLM)
• Multi host changes (Ray)

This PR is to modify vllm_model_wrapper to support PP on torchax path.

• pass intermediate_tensors to step_fun
• also pass in static boolean variable to adapt jax.jit static property
• convert the intermediate tensor between torch and jax.

Tests

E2E test has verified the whole PP implementation works properly.

Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.

[github-actions]

Description

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the past.

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• why is this change being made,
• the problem being solved and any relevant context,
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FIXES: b/123456
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Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.