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/gcore-shaders/src/blending.rs

@@ -66,7 +66,7 @@ impl AlphaBlending {
 }
 
 #[repr(i32)]
-#[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash)]
+#[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash, bytemuck::NoUninit)]
 #[cfg_attr(feature = "std", derive(dyn_any::DynAny, specta::Type, serde::Serialize, serde::Deserialize))]
 pub enum BlendMode {
 	// Basic group