Shaders: runtime and shader node codegen (#2985)

* shader-rt: initial

* shader-rt: fix recursion when generating shader node

* shader-rt: replace gpu node's args and ret types with `Raster<GPU>`

* shader-rt: properly cfg out the gpu node

* shader-rt: fix `impl Context` in the wrong places

* shader-rt: disable gpu blend node, needs two images

* shader-rt: connect shader runtime

* shader-rt: pass WgpuExecutor by reference

* shader-rt: correct bindings with derpy arg buffer

* shader-rt: manual pipeline layout, fixing errors when bindings got DCE'd

* shader-rt: correct RT format, working invert gpu node

* shader-rt: cleanup codegen with common sym struct

* shader-rt: correct arg buffer handling

* shader-nodes feature: put shader nodes behind feature gate

* shader-nodes feature: rename any `gpu_node` to `shader-node`

* shaders-rt: fix wgpu label name

* shaders-rt: explain fullscreen_vertex coordinates with a drawing

node-graph/wgpu-executor/src/lib.rs

@@ -1,6 +1,8 @@
 mod context;
+pub mod shader_runtime;
 pub mod texture_upload;
 
+use crate::shader_runtime::ShaderRuntime;
 use anyhow::Result;
 pub use context::Context;
 use dyn_any::StaticType;
@@ -18,6 +20,7 @@ use wgpu::{Origin3d, SurfaceConfiguration, TextureAspect};
 pub struct WgpuExecutor {
 	pub context: Context,
 	vello_renderer: Mutex<Renderer>,
+	pub shader_runtime: ShaderRuntime,
 }
 
 impl std::fmt::Debug for WgpuExecutor {
@@ -195,6 +198,7 @@ impl WgpuExecutor {
 		.ok()?;
 
 		Some(Self {
+			shader_runtime: ShaderRuntime::new(&context),
 			context,
 			vello_renderer: vello_renderer.into(),
 		})