Integrate segmentation into mutation summary event flow about dark-patterns

[gunesacar]

* re-segment the element's (old) segment, take snapshot(s) of the new segments

For many elements we cannot find an ancestor that is a segment. Rather it's much more common to have a descendant that is a segment.

I plan to segment the element itself when none of the descendants is a segment.

[gunesacar]

This is implemented in gunesacar/OpenWPM@0090cac

It appears CSS animations cause a ton of mutation summary events (and segmentations) in a short time interval. Since we segment only the relevant elements, segmentation doesn't really take long.
But the amount of data stored per page goes upwards of 200MB in some cases.

Let's see if we can rate limit/throttle these expensive operations. Something like wait at least 100ms for running segmentation for an element should work. Perhaps it's a good idea to open a new issue for that.