Node editor: remember scroll position per material/geonode like inside of node groups

The way it works currently is the last scroll position outside of groups is global rather than per nodetree. The problem is when switching between materials or geonodes, the user often has to manually find and scroll to where they were because the absolute position is different per node tree. This isn't a problem inside of node groups, since they seem to store the last scroll position. I think it would be very useful to extend this to remember the scroll position per nodetree. That way, like the current behavior inside of groups, the relevent and recently viewed areas are retained when switching between node trees.