Update the SaveImage transform to support saving input-output mapping.

[binliunls]

Is your feature request related to a problem? Please describe.
When I run a segmentation bundle like spleen segmentation, I would like to have a new json/yaml/csv file to explicitly show the input-output mapping between images and labels. For example if the input and output folders are like:

--input
   --input_0.nii.gz
   --input_1.nii.gz
   -- ...
   --input_n.nii.gz

--output
   --input_0/input_0_seg.nii.gz
   --input_1/input_1_seg.nii.gz
   --...
   --input_n/input_n_seg.nii.gz

Describe the solution you'd like
A json file with content shown below should be generated if the parameter is specified:

[
    {image: ["/path/to/image/input/input_0.nii.gz"], label: ["/path/to/seg/output/input_0/input_0_seg.nii.gz"]},
    {image: ["/path/to/image/input/input_1.nii.gz"], label: ["/path/to/seg/output/input_1/input_1_seg.nii.gz"]},
    ...,
    {image: ["/path/to/image/input/input_n.nii.gz"], label: ["/path/to/seg/output/input_n/input_n_seg.nii.gz"]},
]

The image and label parameters are set to lists in case there are multiple inputs/outputs.