C#: hide ReadGenFields from the public API (#1690)

Author: RReverser

crates/bindings-csharp/Codegen.Tests/fixtures/server/snapshots/Module#PrivateTable.verified.cs

@@ -183,7 +183,7 @@ public override Scope.Extensions ToExtensions()
 
         extensions.Contents.Append(
             $$"""
-            public void ReadGenFields(System.IO.BinaryReader reader) {
+            void {{iTable}}.ReadGenFields(System.IO.BinaryReader reader) {
                 {{string.Join(
                     "\n",
                     autoIncFields.Select(name =>