Use same Crop for RGB image and depth map

[Victorlouisdg]

Describe the feature you'd like
Currently, you have to a separate Crop for each different input image shape you want to use. E.g:

crop_rgb_left = Crop(observation.image_left.shape, x=x, y=y, w=width, h=height) # 3 channels
crop_depth = Crop(observation.depth_map.shape, x=x, y=y, w=width, h=height)  # 1 channel

However, the amount of channels does not matter for the crop operation, so we could probably handle this internally.