[NN DSL] Convolution not taking account custom strides
https://github.com/mratsim/Arraymancer/blob/7edf23662328c059cd22be4cd08c00556321e4d1/src/nn_dsl/dsl_forwardsugar.nim#L9-L31

Compare to maxpool, conv2d is using the default params for padding and strides: https://github.com/mratsim/Arraymancer/blob/7edf23662328c059cd22be4cd08c00556321e4d1/src/nn/layers/conv2D.nim#L45-L48

