Remove dependency of backend CPU and fix CI
- Remove Backend CPU from CMakeLists.txt, setup.py and CI
 - Add include shared script in build CI
 - Add empty python requirements.txt for CI
 - Generate random matrix in tests instead of loading an image from a path for CI on OVH
 - Update Test to comply with opencv::convertNonZero that requires single channel array in v4.2 (https://docs.opencv.org/4.2.0/d2/de8/group__core__array.html#gaa4b89393263bb4d604e0fe5986723914)
 
Edited  by Thibault Allenet