Improve how ripple effects are handled in dom-filters

[jfroelich]

better ripple effects handling. This ties into knowledge of how a document is modified by all filters. Several filters leave the document in a variety of states without consideration of other filters. For example, if we remove an image, and even if we remove figure/picture, then there is still the possibility that this then results in a leaf node, such as a parent div that is basically empty. In other words the ripple effects are recursive, which changes the perspective of what remove is doing, and in hindsight makes it rather naive and questionable whether it is worth it to even attempt to consider any ripple effects at all.

[jfroelich]

Misc related note: A similar concern is, for example, hidden elements. There is no point to processing hidden elements because those are also removed. This naively goes and considers picture/figure that may be hidden. So the work is redundant because the concerns are separated. The joint concern is basically removal. Which suggests the functional purpose should not be oriented based on whether we are removing an image or some other kind of element, but instead the action of removal of any content in a document. Something like a 'dom-removal' API, of which handling images and associated elements for various reasons is just one concern. One of the reasons I have not really solved it is that the solution ties into the entire design of the content filters as a series of separate passes with separate concerns. The problem is in the approach itself.