Implement node graph gpu execution via vulkano and rust gpu (#870)

* Add Executor abstraction

* Resolve inputs for proto nodes by adding compose nodes

* Add infrastructure for compiling gpu code

* Integrate nodegraph gpu execution into graph-crafter

* Extract graphene core path from env vars

* Make Color struct usable for gpu code

node-graph/gcore/src/raster.rs

@@ -1,8 +1,7 @@
 use crate::Node;
 
-use self::color::Color;
-
 pub mod color;
+use self::color::Color;
 
 #[derive(Debug, Clone, Copy)]
 pub struct GrayscaleColorNode;