Fix source generator exceptions appearing when use "@+internal keyword" as type or namespace name in C# script

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators.Tests/TestData/GeneratedSources/namespace.class_ScriptMethods.generated.cs

@@ -0,0 +1,17 @@
+using Godot;
+using Godot.NativeInterop;
+
+namespace @namespace {
+
+partial class @class
+{
+#pragma warning disable CS0109 // Disable warning about redundant 'new' keyword
+    /// <summary>
+    /// Cached StringNames for the methods contained in this class, for fast lookup.
+    /// </summary>
+    public new class MethodName : global::Godot.GodotObject.MethodName {
+    }
+#pragma warning restore CS0109
+}
+
+}