Cross frame resource tracking

[David Dubois]

We need some way to save what state a resource was in last frame, and issue barrier from that state to the current state

Maybe a StateTracker class that handles all state tracking?

[David Dubois]

I've done a bit on this. I've added a way to extract a texture's most recent usage token from the render graph, and a way to set the usage token of a texture without issuing a barrier. This is sufficient for basic things like preserving the depth buffer across frames