Fix/aidge backend opencv

Context

(Summarize the problem you are facing and the solution you propose to resolve the issue)

(If possible add link to a gitlab issue #...)

(Describe the issue - you can paste any logs or/screenshots, the link to the line of code that might be responsible for the problem)

(In the case of feature addition, describe the context arround the need of this addition)

Modified files

(Summarize the changes you made for each modified file - example:

• DeepNet.hpp and DeepNet.cpp, add several learning methods;
• learn.cpp, to include the learning functions inside the main function;
• test_conv.cpp, to correct the new syntax in the tests; )

Detailed major modifications

(Explain the non-trivial changes you made in the modified files)

(Specify if you made an important technical decision which should be added to the wiki https://gitlab.eclipse.org/groups/eclipse/aidge/-/wikis/home or the documentation)

TODO

(List the changes that need to be done to track the progress of the MR, you need to update the list when committing !)

• NOT DONE
• DONE
• TO DO