COMP: update OPENCV from 4.10 to 4.12

New function precondition on "Mat.at" lead to assertion on a Learning test about mismatch data type. Tried different solutions:

• Adapt the type of the Mat with opencv SafeType fonction (https://docs.opencv.org/4.x/d7/db8/namespacecv_1_1traits.html) but it does not work, assertion later
• Try with opencv Type and std::make_signed, but make_signed is not implemented for floating types, thus compilation fails. Try a solution from stackoverflow https://stackoverflow.com/questions/16377736/stdmake-signed-that-accepts-floating-point-types but it leads to ununderstandable overengineered solution