SVS: Detect label and macro if no image description

[dgault]

This is a rather simplistic attempt to deal with the issue detected in #3757
If no image description is present then it will try to treat the series as a label or macro.

Fixes #3757

To test:

• All existing builds and repo tests should remain green
• Test manually with the new sample file from the thread (also included in the new config PR)
• Test with the sample files impacted by the original PR in https://github.com/openmicroscopy/data_repo_config/pull/503

[sbesson]

Tested using both the newly provided SVS sample as well as former samples using for #3733. Everything works as expected with macro and label images detected appropriately.

In the absence of additional representative samples, this feels like the best compromise allowing to fix the regression for some SVS variants reported in #3757 while preserving the improvements introduced in 6.8.0

[imagesc-bot]

This pull request has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/remove-label-and-macro-from-a-wsi/45630/6