This speeds up drawing of the UI of the Geometry Nodes modifier, especially for
very large node trees like in the files from #146949.
A couple previous commits and #147883 speed up the inferencing significantly
already. However, there is a certain limit to how fast this can be on large
complex node trees. While there is some more optimization potential, this patch
implements a cache on the Geometry Nodes modifier level. This means that as long
as the inputs and the node tree stays the same, the inferencing only has to
happen once, instead of on every redraw.
The main difficulty with this cache is that we don't have a good way to
invalidate it eagerly when any of the modifier inputs changes. That can
hopefully become simpler with #138117. For now, we have to check all input
values on redraw to check if anything has changed compared to the last redraw
and recompute the cache if there is any change.
Pull Request: https://projects.blender.org/blender/blender/pulls/147930
d690ffd44f