Blender Git Loki

Fix T60900, T61111, T61963: node values stuck after clearing keyframes.

This removes special dependency graph code that was intended to avoid GPU
shader recompiles by preserving the node tree and GPU material in specific
cases. This is no longer needed now that we have a general shader pass
cache that compares the generated shader code. The GPU material is already
being freed in material and world eval as well, so there's no point.

Note also that GPU materials are now safe to free from threads, actual
OpenGL buffer freeing happens delayed.