Shaders: add gcore-shaders and make graster-nodes no-std (#2925)

* gcore-shaders: add crate, move `color` and `blending` from gcore

* gcore-shaders: move `AsU32`

* gcore-shaders: move `ChoiceType`, switch `Cow` for `&str`, adjust node macro

* gcore-shaders: move `registry::types`

* gcore-shaders: move `context::Ctx`

* raster-nodes: make it `no_std` with `std` feature

* gcore-shaders: fix doctest

node-graph/gcore-shaders/src/registry.rs

@@ -0,0 +1,24 @@
+pub mod types {
+	/// 0% - 100%
+	pub type Percentage = f64;
+	/// -100% - 100%
+	pub type SignedPercentage = f64;
+	/// -180° - 180°
+	pub type Angle = f64;
+	/// Ends in the unit of x
+	pub type Multiplier = f64;
+	/// Non-negative integer with px unit
+	pub type PixelLength = f64;
+	/// Non-negative
+	pub type Length = f64;
+	/// 0 to 1
+	pub type Fraction = f64;
+	/// Unsigned integer
+	pub type IntegerCount = u32;
+	/// Unsigned integer to be used for random seeds
+	pub type SeedValue = u32;
+	/// DVec2 with px unit
+	pub type PixelSize = glam::DVec2;
+	/// String with one or more than one line
+	pub type TextArea = String;
+}