Add rendernode performance monitoring

This is a branch that adds per-rendernode CPU and GPU performance counters for the Vulkan renderer via GSK_DEBUG=perf.

For now it's unclear what to do when we get the annotated rendernode, as that rendernode is only available after the GPU has finished executing, so it just dumps it to stdout for now.
It's also unclear how to expose this information as I don't want to put it into API, but just having it in the inspector seems limited. For now, we add it as the debug node's message, which makes it at least available for human consumption in the rendernode serialization.