FIX: Conv[DepthWise] forward implementation and add tests

Context

Call to Conv(kernel_size=[3,3], stride = [2,2]) was returning a random Tensor.

After careful review, it appears the new Conv implementation !101 (merged), if faster, splits the computation in more small cases that were not all tested. For example, Conv(kernel_size=[3,3], stride = [2,2]) and Conv(kernel_size=[3,3], stride = [2,2]) don't go through the same loop.

This MR adds tests for each of the following cases for Conv and ConvDepthWise:

• kernel [3, 3]
  • no stride, no dilation
  • stride [2,2], no dilation
  • stride [2,2], dilation [2,2]
• kernel [1,1]
  • no stride, no dilation
  • stride [3,3], no dilation
  • stride [3,3], dilation [2,2]
• kernel [5,5]
  • no stride, no dilation
  • stride [2,2], no dilation
  • stride [2,2], dilation [2,2]

Some issues were found thanks to these new tests and fixed.