Support checking select_fn on "all" channels in generate_spatial_bounding_box

[function2-llx]

Is your feature request related to a problem? Please describe.

When apply transform like CropForeground to a multichannel image, the bounding box is determined by checking select_fn on "any" channel. However, in many cases, we may want to check it on "all" channels, e.g., when cropping RGB images, we discard background pixels with all 3 channels being zero, instead of pixels with any one of the channel being zero.

MONAI/monai/transforms/utils.py

Line 1029 in 8c709de

data = select_fn(data).any(0)

Describe the solution you'd like
Add some option indicating that we should call select_fn(data).all(0) in the line of code above.

[function2-llx]

After rethinking, I think I made a mistake. The current implementation is exactly what I want. I apologize for the confusion.