feat: add backend param for triton serving

[gujingit]

Feature: support vllm、 tensorrt-llm backend for triton serving.

vllm backend

arena serve triton \
 --backend=vllm \
 --name=triton-vllm \
 --namespace=default \
 --cpu=6 \
 --memory=12Gi \
 --gpus=1 \
 --data=model-pvc:/mnt/pvc/ \
 --model-repository=/mnt/pvc/model_repository

trt-llm

arena serve triton \
 --backend=trt-llm \
 --name=triton-trt-llm \
 --namespace=default \
 --cpu=6 \
 --memory=12Gi \
 --gpus=1 \
 --data=model-pvc:/mnt/pvc/ \
 --model-repository=/mnt/pvc/model_repository

[gujingit]

/assign @Syulin7

[Syulin7]

@gujingit Thanks! Can you submit a new PR to update the document?

[Syulin7]

/lgtm
/approve

[google-oss-prow]

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This pull-request has been approved by: gujingit, Syulin7

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