Import Conv operator: Add zeroed bias producer when no bias is provided.

Context

When importing the Resnet18 model (for example), some convolution doesn't provide the optional bias matrix. For inference Aidge require these input to be provided hence require additional user setup to use the model.

I propose to create a zeroed Producer in place of the bias when loading the ONNX model to simplify loading and forward steps.

Modified files

• aidge_onnx/node_import/onnx_converters/conv.py;

Detailed major modifications

When a conv operator is loaded if the optional bias is not provided, a zeroed Producer of the size of the output node is created.

TODO

• Added zeroed producer when bias not provided