[onnx] Constant operator badly imported for 0-dimension arrays

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What commit version of aidge do you use

• aidge_core: 0.2.2
• aidge_onnx: 0.2.2

Problem description

When running the test script aidge_onnx/unit_tests/test_import_export.py, a MobileNet-v2 model is downloaded from here https://github.com/onnx/models/raw/69d69010b7ed6ba9438c392943d2715026792d40/Computer_Vision/mobilenetv2_050_Opset18_timm/mobilenetv2_050_Opset18.onnx

However, it appears many Constant nodes are badly imported as GenericOperators instead of Producers. Define the expected behavior.

Reproducible example code

Run aidge_onnx/unit_tests/test_import_export.py