This is a better and more general fix for T92511 and T92508 than
the ones that I committed before.
Previously, we tagged caches dirty when first accessing attributes.
This led to incorrect caches when under some circumstances. Now
cache invalidation is part of `OutputAttribute.save()`.
A nice side benefit of this change is that it may make things more
efficient in some cases, because we don't invalidate caches when
they don't have to be invalidated.
Differential Revision: https://developer.blender.org/D13009
cf771807b7