Fix C# examples in documentation

- Fix documentation after C# renames.
- Add missing `partial` in C# class declarations.
- Change `delta` parameter type to `double` in C#.
- Ensure parameters match base declaration.
- Use `$` string interpolation in C#.
- Fix invalid or outdated C# code.
- Changed some examples to follow our style guide more closely.

doc/classes/EditorScenePostImport.xml

@@ -10,12 +10,14 @@
 		[gdscript]
 		@tool # Needed so it runs in editor.
 		extends EditorScenePostImport
+
 		# This sample changes all node names.
 		# Called right after the scene is imported and gets the root node.
 		func _post_import(scene):
 		    # Change all node names to "modified_[oldnodename]"
 		    iterate(scene)
 		    return scene # Remember to return the imported scene
+
 		func iterate(node):
 		    if node != null:
 		        node.name = "modified_" + node.name
@@ -30,17 +32,18 @@
 		[Tool]
 		public partial class NodeRenamer : EditorScenePostImport
 		{
-		    public override Object _PostImport(Node scene)
+		    public override GodotObject _PostImport(Node scene)
 		    {
 		        // Change all node names to "modified_[oldnodename]"
 		        Iterate(scene);
 		        return scene; // Remember to return the imported scene
 		    }
+
 		    public void Iterate(Node node)
 		    {
 		        if (node != null)
 		        {
-		            node.Name = "modified_" + node.Name;
+		            node.Name = $"modified_{node.Name}";
 		            foreach (Node child in node.GetChildren())
 		            {
 		                Iterate(child);