Shaders: graster-nodes no-std prep (#2924)

* raster-nodes: remove commented out index node

* raster-nodes: move `CubicSplines` to separate mod

* raster-nodes: create `mod blending_nodes` and move assoc nodes

* raster-nodes: move node `gradient_map` to its own mod

node-graph/graster-nodes/src/adjust.rs

@@ -0,0 +1,35 @@
+use graphene_core::Color;
+use graphene_core::gradient::GradientStops;
+use graphene_core::raster_types::{CPU, RasterDataTable};
+
+pub trait Adjust<P> {
+	fn adjust(&mut self, map_fn: impl Fn(&P) -> P);
+}
+impl Adjust<Color> for Color {
+	fn adjust(&mut self, map_fn: impl Fn(&Color) -> Color) {
+		*self = map_fn(self);
+	}
+}
+impl Adjust<Color> for Option<Color> {
+	fn adjust(&mut self, map_fn: impl Fn(&Color) -> Color) {
+		if let Some(v) = self {
+			*v = map_fn(v)
+		}
+	}
+}
+impl Adjust<Color> for GradientStops {
+	fn adjust(&mut self, map_fn: impl Fn(&Color) -> Color) {
+		for (_pos, c) in self.iter_mut() {
+			*c = map_fn(c);
+		}
+	}
+}
+impl Adjust<Color> for RasterDataTable<CPU> {
+	fn adjust(&mut self, map_fn: impl Fn(&Color) -> Color) {
+		for instance in self.instance_mut_iter() {
+			for c in instance.instance.data_mut().data.iter_mut() {
+				*c = map_fn(c);
+			}
+		}
+	}
+}