Add support for tracked segmentation masks?

[sfmig]

With tools like SAM2 that track segmentation masks in videos, this may be a nice addition to our set of accepted input data.

Segmentation masks are usually represented as RLE (Run length encoding):

• an example file with description (click Overview , then Submission file section)
• a nice (video) explanation here -- see "Segmentation" (RLE - Run Length Encoding) bookmark

Maybe we can consider to link masks to bounding boxes too?

We may want to check Annolid - an annotation and tracking tool centred around instance segmentation

[niksirbi]

@gchindemi has also expressed strong interest in movement supporting this type of tracking data. Given the growing popularity of models like SAM, I think the appetite for this sort of thing will keep growing, which means we should probably implement this.