Restructure GPU execution to model GPU pipelines in the node graph (#1088)

* Start implementing GpuExecutor for wgpu

* Implement read_output_buffer function

* Implement extraction node in the compiler

* Generate type annotations during shader compilation

* Start adding node wrapprs for graph execution api

* Wrap more of the api in nodes

* Restructure Pipeline to accept arbitrary shader inputs

* Adapt nodes to new trait definitions

* Start implementing gpu-compiler trait

* Adapt shader generation

* Hardstuck on pointer casts

* Pass nodes as references in gpu code to avoid zsts

* Update gcore to compile on the gpu

* Fix color doc tests

* Impl Node for node refs

node-graph/gcore/src/ops.rs

@@ -1,5 +1,5 @@
 use core::marker::PhantomData;
-use core::ops::Add;
+use core::ops::{Add, Mul};
 
 use crate::Node;
 
@@ -30,6 +30,27 @@ where
 	first + second
 }
 
+pub struct MulParameterNode<Second> {
+	second: Second,
+}
+
+#[node_macro::node_fn(MulParameterNode)]
+fn flat_map<U, T>(first: U, second: T) -> <U as Mul<T>>::Output
+where
+	U: Mul<T>,
+{
+	first * second
+}
+
+#[cfg(feature = "std")]
+struct SizeOfNode {}
+
+#[cfg(feature = "std")]
+#[node_macro::node_fn(SizeOfNode)]
+fn flat_map(ty: crate::Type) -> Option<usize> {
+	ty.size()
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
 pub struct SomeNode;
 #[node_macro::node_fn(SomeNode)]