pytests: add test that evaluates front sensor's test pattern
requested to merge martin.kepplinger/librem5-devkit-tools:test_cameras_test_patterns into pureos/byzantium
for now only for the seflie cam.
If the python code-cleanup stuff is done ( with @guido.gunther ) and when the rear camera is fixed for v6.0 based kernels ( linux#440 (closed) ) adding the rear cam function is trivial (if implemented in the driver).
Fixes: #50 (closed)