Shaders: more graster-nodes no-std fixups (#3090)

* gcore-shaders: fix missing `num-traits/libm` features

* graster-nodes: fix missing cfg on use statements

* shaders: use unchecked Color constructors

* graster-nodes: remove async from shader nodes not needing it

* gcore-shaders: remove explicit fn pointer

* graster-nodes: make kurbo std-only

* graster-nodes: replace glam reexport with normal dep

* gcore: impl Display for ProtoNodeIdentifier

* unify glam workspace dep

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

@@ -1,6 +1,6 @@
 use core::fmt::Display;
 use core::hash::{Hash, Hasher};
-#[cfg(target_arch = "spirv")]
+#[cfg(not(feature = "std"))]
 use num_traits::float::Float;
 
 #[derive(Debug, Clone, Copy, PartialEq)]