Exploring Rust for Vulkan drivers

I don't expect to see any actual Mesa Vulkan drivers in Rust for a few years yet. My current goal is merely to explore the possibility. When the time comes that someone does choose to write a Vulkan driver in Rust, I want us to be ready. This exploration may also be useful for informing the Rust community about language features which would make the task easier. Converting existing Vulkan drivers to Rust is an explicit non-goal at this time.

Rust seems everywhere.