MLBEDSW-7283: Add opt cases for strided CONV2D

* Implement a general optimization solution for strided CONV2D that
  supports a stride_w with no upper bound.
* Implement filter zero padding to allow for optimization in those cases
  in which the filter width is not divisible by the stride width.
  E.g.: Filter width = 8, stride width = 3 ->
        Filter width = 8 + 1 (0 padding) = 9, stride width = 3
* Implement partial optimization to reduce the stride to hw supported
  strides (i.e. 2 and 3) when optimizing to reach a stride = 1 is not
  possible due to the IFM width not being divisible by the stride width.
* Implement optimization for when SAME padding is used. If the pre-opt
  and post-opt padding do not match, add zero padding to the filter so
  that the post-opt IFM padding matches.

Change-Id: Ia66b0d107281fa9993f6bf4d0c26627ee743253b
Signed-off-by: Raul Farkas <raul.farkas@arm.com>