Auto-generate enum type widget boilerplate for radio buttons and dropdown menus (#2589)

* First draft of factoring out the dropdown boilerplate

* Add proc macro for enum boilerplate

* Detect whether to say `crate` or the name

* Clean up the input and naming of the enum macro

* Rename a file

* Do the rename of code too

* Use the attribute-driven selection of radio vs dropdown

* Add a metadata struct and tooltips

* Move the new traits to a better place.

* Use ChoiceType, part 1

* Use ChoiceType, part 2

* Introduce a builder API for choice widgets

* Start using the new new API

* DomainWarpType should be a dropdown still

* Handle the case where a node property can never have a socket

* Rustfmt

* Code review

* Update stable node IDs in test

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

node-graph/gcore/src/registry.rs

@@ -1,5 +1,6 @@
 use crate::{Node, NodeIO, NodeIOTypes, Type, WasmNotSend};
 use dyn_any::{DynAny, StaticType};
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::marker::PhantomData;
 use std::ops::Deref;
@@ -53,6 +54,33 @@ pub struct FieldMetadata {
 	pub number_mode_range: Option<(f64, f64)>,
 }
 
+pub trait ChoiceTypeStatic: Sized + Copy + crate::vector::misc::AsU32 + Send + Sync {
+	const WIDGET_HINT: ChoiceWidgetHint;
+	const DESCRIPTION: Option<&'static str>;
+	fn list() -> &'static [&'static [(Self, VariantMetadata)]];
+}
+
+pub enum ChoiceWidgetHint {
+	Dropdown,
+	RadioButtons,
+}
+
+/// Translation struct between macro and definition.
+#[derive(Clone, Debug)]
+pub struct VariantMetadata {
+	/// Name as declared in source code.
+	pub name: Cow<'static, str>,
+
+	/// Name to be displayed in UI.
+	pub label: Cow<'static, str>,
+
+	/// User-facing documentation text.
+	pub docstring: Option<Cow<'static, str>>,
+
+	/// Name of icon to display in radio buttons and such.
+	pub icon: Option<Cow<'static, str>>,
+}
+
 #[derive(Clone, Debug)]
 pub enum RegistryWidgetOverride {
 	None,