Refactor GDScript/C# script templates logic to be editor-only

Not a full refactor as it still goes through ScriptLanguage so it's hacky,
but at least it can now compile without this.

modules/mono/editor/script_templates/Node/default.cs

@@ -0,0 +1,17 @@
+// meta-description: Base template for Node with default Godot cycle methods
+
+using _BINDINGS_NAMESPACE_;
+using System;
+
+public partial class _CLASS_ : _BASE_
+{
+    // Called when the node enters the scene tree for the first time.
+    public override void _Ready()
+    {
+    }
+
+    // Called every frame. 'delta' is the elapsed time since the previous frame.
+    public override void _Process(float delta)
+    {
+    }
+}