This patch removes no-op node editor preview code (`PR_NODE_RENDER`) and most calls to `BKE_node_preview_init_tree`. The only remaining call is in the compositor. - Shader nodes previews don't seem to do anything. - In-node previews for the texture node system doesn't work either. This is a first step to refactoring to remove `preview_xsize`, `preview_ysize`, and `prvr` from nodes in DNA, aligned with the general goal of removing runtime/derived data from data structs. Differential Revision: https://developer.blender.org/D13578