This patch generalizes node tree subtypes to be usable for node trees other than Geometry Nodes. In particular, this: - Renames SpaceNode.geometry_nodes_type to node_tree_sub_type, which now store a tree type-specific enum. - Renames SpaceNode.geometry_nodes_tool_tree to selected_node_group, which now stores any context-less tree of any type. This breaks the python API due to renaming. Pull Request: https://projects.blender.org/blender/blender/pulls/144544