Add --backend TRT_LLM_BUILDER option to truss init

[philipkiely-baseten]

🚀 What

Right now, the default model.py in Truss causes an error when trying to push with the engine builder. @htrivedi99 ran into this issue during testing.

This new option for the --backend flag in truss init solves this by providing a better default model.py that does not cause an error.

I also updated the default config when using this option with scaffold for the trt_llm.build.

💻 How

🔬 Testing

Please test by creating a Truss with this model.py and using the engine builder.

pip install .
truss init --backend TRT_LLM_BUILDER --name "init test truss" init-test-truss