fix: identify ConstantOfShape ONNX nodes as constant values

[RomanBredehoft]

this PR is in draft until we find a proper solution, as the initial suggestion is not right (ConstantOfShape are not real constants, they have an input coming in)

a model that contains a "ConstantOfShape" node can trigger an obscure AttributeError: 'RawOpOutput' object has no attribute 'quantizer' in the QuantizedAdd operator

closes https://github.com/zama-ai/concrete-ml-internal/issues/4406

[andrei-stoian-zama]

Nicely done

[github-actions]

Coverage failed ❌

Coverage details

---------- coverage: platform linux, python 3.8.18-final-0 -----------
Name                                                Stmts   Miss  Cover   Missing
---------------------------------------------------------------------------------
src/concrete/ml/onnx/ops_impl.py                      357      5    99%   88, 1552, 2060, 2065-2066
src/concrete/ml/quantization/base_quantized_op.py     303      1    99%   657
---------------------------------------------------------------------------------
TOTAL                                                7522      6    99%

57 files skipped due to complete coverage.

[RomanBredehoft]

unfortunately, the issue started to be more complex than I initially thought, and the solution provided does not entirely fix the issue : https://github.com/zama-ai/concrete-ml-internal/issues/4413