MLBEDSW-9742 Batched conv2d produces output diff

 - An output diff occurred because decomposition was not done for
convolutions when batch was greater than 1
 - Add check to CanRunOnHardware checking for batch for conv
 - Use SliceShape instead of full shape in DecomposeConv2D and
DecomposeDepthwiseConv2D

Change-Id: Ic932ad329327beea75df8e76b48d737e53aa3cb0
Signed-off-by: Johan Alfven <johan.alfven@arm.com>