Support CodeAction.NestedActions via light-up

Closes #1136

src/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.Analyzer.Testing/CodeActionTest`1.cs

@@ -164,7 +164,7 @@ namespace Microsoft.CodeAnalysis.Testing
                 for (var i = builder.Count - 1; i >= 0; i--)
                 {
                     var action = builder[i];
-                    var nestedActions = action.NestedCodeActions();
+                    var nestedActions = action.NestedActions();
                     if (!nestedActions.IsEmpty)
                     {
                         builder.RemoveAt(i);

src/Microsoft.CodeAnalysis.Testing/Microsoft.CodeAnalysis.Analyzer.Testing/Extensions/CodeActionExtensions.cs

@@ -11,13 +11,29 @@ namespace Microsoft.CodeAnalysis.Testing
 {
     internal static class CodeActionExtensions
     {
+        private static readonly Func<CodeAction, ImmutableArray<CodeAction>> s_nestedActions =
+            LightupHelpers.CreatePropertyAccessor<CodeAction, ImmutableArray<CodeAction>>(
+                typeof(CodeAction),
+                nameof(NestedActions),
+                defaultValue: default);
+
         private static readonly Func<CodeAction, ImmutableArray<CodeAction>> s_nestedCodeActions =
             LightupHelpers.CreatePropertyAccessor<CodeAction, ImmutableArray<CodeAction>>(
                 typeof(CodeAction),
-                nameof(NestedCodeActions),
+                "NestedCodeActions",
                 defaultValue: ImmutableArray<CodeAction>.Empty);
 
-        public static ImmutableArray<CodeAction> NestedCodeActions(this CodeAction action)
-            => s_nestedCodeActions(action);
+        public static ImmutableArray<CodeAction> NestedActions(this CodeAction action)
+        {
+            // CodeAction.NestedCodeActions was renamed to CodeAction.NestedActions in
+            // https://github.com/dotnet/roslyn/pull/71327
+            var nestedActions = s_nestedActions(action);
+            if (nestedActions.IsDefault)
+            {
+                nestedActions = s_nestedCodeActions(action);
+            }
+
+            return nestedActions;
+        }
     }
 }