Rely on the depsgraph to detect scene updates, using the `view_update` callback. Remove `SceneHandle` and `scene_sync`. Remove `reset_recalc_flag`. Remove most `sampling.reset()` calls and their related logic, and move the remaining ones to `Instance`. Re-sync lights on `light_threshold` changes. Pull Request: https://projects.blender.org/blender/blender/pulls/115758