[Bug] bounding_box() returns wrong z start and depth values for 2D images

[thawn]

Pre-requist tasks

• [x] My device drivers are up to date.
• [x] The troublemaking solutions did not solved my issue.

Describe the bug the results of bounding_box() are wrong for 2-d images

To Reproduce

import pyclesperanto as cle
import pyclesperanto_prototype as clep
import numpy as np

#create sample image
image = np.zeros((100, 100))
image[10:30, 20:80] = 1

#measure the bounding box with pyclesperanto
cle.bounding_box(image) # returns [20.0, 10.0, 10.0, 79.0, 29.0, 1.0]

#measure the bounding box with pyclesperanto_prototype
clep.bounding_box(image) # returns [20.0, 10.0, 0, 79.0, 29.0, 0]

**Expected behavior**
for a 2-D image, the bounding box z start and depth values should both be 0

**Configuration details:**
 - OS: [e.g. MacOS 12.7.2]
 - Device: [Apple M1 Max]
 - Device type: [Integrated GPU]

[thawn]

Cool thanks, Stephane 🎉