quark.onnx.tools.convert_fp16_to_bfp16

Convert tensor float16 type in the ONNX ModelProto input to tensor bfp16.

Use the convert_fp16_to_bfp16.py to convert a float16 model to a bfp16 model:

` python convert_fp16_to_bfp16.py --input $FLOAT_16_ONNX_MODEL_PATH --output $BFP_16_ONNX_MODEL_PATH `