TAO Converter Provide three optimization profiles for pointpillar

To narrow down, please refer to tao_toolkit_recipes/tao_forum_faq/FAQ.md at main · NVIDIA-AI-IOT/tao_toolkit_recipes · GitHub to change the etlt file to onnx file.
Then please refer to TRTEXEC with PointPillars - NVIDIA Docs to use trtexec to generate tensorrt engine.