Add Component2 / AbstractComponent2 annotations

+ And deprecate the v1 ones

lib/src/component_declaration/annotations.dart

@@ -69,6 +69,9 @@ class State implements TypedMap {
 ///     }
 ///
 /// Must be accompanied by a [Factory] and [Props] declaration.
+///
+/// __Deprecated.__ Use the [Component2] annotation alongside `UiComponent2` / `UiStatefulComponent2` instead.
+@Deprecated('4.0.0')
 class Component {
   /// Whether the component clones or passes through its children and needs to be
   /// treated as if it were the wrapped component when passed in to [over_react.isComponentOfType].
@@ -104,6 +107,51 @@ class Component {
   });
 }
 
+/// Annotation used with the `over_react` builder to declare a `UiComponent2` class for a component.
+///
+///     @Component2()
+///     class FooComponent extends UiComponent2<FooProps> {
+///       render() => Dom.div()(props.bar);
+///     }
+///
+/// Must be accompanied by a [Factory] and [Props] declaration.
+class Component2 implements Component {
+  /// Whether the component clones or passes through its children and needs to be
+  /// treated as if it were the wrapped component when passed in to `isComponentOfType`.
+  @override
+  final bool isWrapper;
+
+  /// The component class of this component's "parent type".
+  ///
+  /// Used to enable inheritance in component type-checking in `isComponentOfType`.
+  ///
+  /// E.g., if component `Bar` is a subtype of component `Foo`:
+  ///
+  ///     @Factory()
+  ///     UiFactory<...> Foo = _$Foo;
+  ///     ...
+  ///     @Component2()
+  ///     class FooComponent ... {...}
+  ///
+  ///     @Factory()
+  ///     UiFactory<...> Bar = _$Bar;
+  ///     ...
+  ///     @Component2(subtypeOf: FooComponent)
+  ///     class BarComponent ... {...}
+  ///
+  /// then:
+  ///
+  ///     isComponentOfType(Bar()(), Bar); // true (due to normal type-checking)
+  ///     isComponentOfType(Bar()(), Foo); // true (due to parent type-checking)
+  @override
+  final Type subtypeOf;
+
+  const Component2({
+      this.isWrapper: false,
+      this.subtypeOf
+  });
+}
+
 /// Annotation used with the `over_react` builder to declare an abstract [UiProps] class for an abstract component.
 ///
 /// Props are declared as fields, which act as stubs for generated getters/setters that proxy Map key-value pairs.
@@ -140,10 +188,21 @@ class AbstractState implements TypedMap {
 ///
 ///     @AbstractComponent()
 ///     abstract class QuxComponent<TProps extends QuxProps> extends UiComponent<TProps> {}
+///
+/// __Deprecated.__ Use the [AbstractComponent2] annotation alongside `UiComponent2` / `UiStatefulComponent2` instead.
+@Deprecated('4.0.0')
 class AbstractComponent {
   const AbstractComponent();
 }
 
+/// Annotation used with the `over_react` builder to declare an abstract `UiComponent2` class for an abstract component.
+///
+///     @AbstractComponent2()
+///     abstract class FooComponent<TProps extends QuxProps> extends UiComponent2<TProps> {}
+class AbstractComponent2 implements AbstractComponent {
+  const AbstractComponent2();
+}
+
 /// Annotation used with the `over_react` builder to declare a mixin for use in a [UiProps] class.
 ///
 /// Props are declared as fields, which act as stubs for generated getters/setters that proxy Map key-value pairs.

lib/src/component_declaration/builder_helpers.dart

@@ -130,6 +130,9 @@ mixin _GeneratedUiComponent2Stubs<TProps extends UiProps>
   TProps typedPropsFactoryJs(JsBackedMap propsMap) => throw new UngeneratedError(member: #typedPropsFactoryJs);
 }
 
+/// See: [component_base.UiComponent2]
+///
+/// Use with the over_react builder via the `@Component2()` ([annotations.Component2]) annotation.
 abstract class UiComponent2<TProps extends UiProps>
     extends component_base.UiComponent2<TProps>
     with
@@ -142,6 +145,9 @@ abstract class UiComponent2<TProps extends UiProps>
   }
 }
 
+/// See: [component_base.UiStatefulComponent2]
+///
+/// Use with the over_react builder via the `@Component2()` ([annotations.Component2]) annotation.
 abstract class UiStatefulComponent2<TProps extends UiProps, TState extends UiState>
     extends component_base.UiStatefulComponent2<TProps, TState>
     with