[ROCm] Effort to reduce the number of environment variables in command line

[hongxiayang]

This is to set two environment variables in the Docker file so that users can reduce the number of environment variables when running scripts.

ENV that can improve safe tensor loading, and end-to-end time

ENV SAFETENSORS_FAST_GPU=1

ENV that needed for multi-process on cuda-like platform

ENV VLLM_WORKER_MULTIPROC_METHOD=spawn

[github-actions[bot]]

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[houseroad]

Can we add a test plan?

[hongxiayang]

Can we add a test plan?

Added the test plan in the description of the pull request