Add flashinfer_python to CUDA wheel requirements

[mgoin]

Purpose

We have installed flashinfer by default in the docker image for a long time, but now as we use flashinfer for many critical kernels for NVIDIA Blackwell we should consider adding it to the default CUDA dependencies.

The flashinfer-python wheel by default does not include pre-compiled kernels, so users will JIT at runtime.

Test Plan

See if there are any conflicts in CI with the Dockerfile's manual AOT build

Test Result

[github-actions]

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[gemini-code-assist]

Code Review

This pull request adds flashinfer_python as a dependency for CUDA environments. While this is useful for local development, it introduces a conflict with the existing Docker build process, which builds FlashInfer from source. This leads to a redundant installation and a version mismatch, making the Docker build fragile and potentially incorrect. I've recommended a solution to conditionally exclude this dependency during the Docker build to resolve the conflict.

[Swipe4057]

up https://pypi.org/project/flashinfer-python/0.2.9rc1/

[houseroad]

Looks good.