Blender Git Loki

Cleanup: Remove runtime uiBlock pointer from nodes

Code is simpler when the uiBlocks used during drawing are simply
stored in an array. Additionally, looping can be simpler when we use
an vector to hold a temporary copy of the tree's linked list of nodes.

This patch also slightly changes how uiBlocks are "named" in
`node_uiblocks_init`. Now it uses the node name instead of the
pointer, which is helpful so we rely less on the node's address.

Differential Revision: https://developer.blender.org/D13540