Add validate tests for CLConvolutionLayer and CLGEMMConvolutionLayer with post ops

* Add validate tests
* Restrict post ops support in ClGemmConv2d to only those that do not
  need im2col or col2im. In practice this means we only support post ops
  in conv1x1 with stride = 1, dilation = 1 and data layout = NHWC

Resolves COMPMID-4435

Change-Id: I1fdf0c5d565a4624857250075ac76db35c2f383b
Signed-off-by: SiCongLi <sicong.li@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/6573
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/arm_compute/core/experimental/IPostOp.h b/arm_compute/core/experimental/IPostOp.h
index 178c83a..567a402 100644
--- a/arm_compute/core/experimental/IPostOp.h
+++ b/arm_compute/core/experimental/IPostOp.h
@@ -71,6 +71,15 @@
  *          * post_op_arg1 = [1, 1, 34] is allowed: broadcast in dims 0 and 1
  *          * post_op_arg1 = [14, 15, 34] is NOT allowed: broadcast widens the dst tensor
  *
+ * @note: On Data layout
+ *      All post ops are data layout agnostic. This means post ops do not have an inherent idea of "width", "height" and so on.
+ *      Should we want to perform a post op with 2 tensors of different data layouts (where data layouts are significant to both),
+ *      then we need to perform necessary permutation op beforehand to unify their data layout before they can be fused with a post op
+ *
+ *      Note although post ops themselves should be able to support any data layout, the main op they fuse to may impose
+ *      additional restrictions in the presence of post ops. For example, the implementation of a gemm op may only allow
+ *      NHWC data layout if post ops are provided. Such restrictions are main op implementation specific.
+ *
  *  @note: PostOps do not own any resources pointed to by TensorRelatedT if it's a pointer type
  *  @note: If TensorRelatedT points to a resource, IPostOp assumes that resource is valid throughout its lifetime
  *        and the lifetime of its copies. This is almost guaranteed as IPostOp is only meant to be used at configure time