Blender Git Loki

Fix T87536: incorrect socket types in reroute nodes

This refactors and fixes the code that propagates socket types
through reroute nodes. In my tests it is faster than the previous
code. The difference becomes larger the more reroute nodes
there are, because the old code had O(n^2) runtime, while the
new code runs in linear time.

Differential Revision: https://developer.blender.org/D12716