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- Fix invalid or outdated C# code.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/Geometry2D.xml

@@ -160,14 +160,13 @@
 				var polygon = PackedVector2Array([Vector2(0, 0), Vector2(100, 0), Vector2(100, 100), Vector2(0, 100)])
 				var offset = Vector2(50, 50)
 				polygon = Transform2D(0, offset) * polygon
-				print(polygon) # prints [Vector2(50, 50), Vector2(150, 50), Vector2(150, 150), Vector2(50, 150)]
+				print(polygon) # prints [(50, 50), (150, 50), (150, 150), (50, 150)]
 				[/gdscript]
 				[csharp]
 				var polygon = new Vector2[] { new Vector2(0, 0), new Vector2(100, 0), new Vector2(100, 100), new Vector2(0, 100) };
 				var offset = new Vector2(50, 50);
-				// TODO: This code is not valid right now. Ping @aaronfranke about it before Godot 4.0 is out.
-				//polygon = (Vector2[]) new Transform2D(0, offset).Xform(polygon);
-				//GD.Print(polygon); // prints [Vector2(50, 50), Vector2(150, 50), Vector2(150, 150), Vector2(50, 150)]
+				polygon = new Transform2D(0, offset) * polygon;
+				GD.Print((Variant)polygon); // prints [(50, 50), (150, 50), (150, 150), (50, 150)]
 				[/csharp]
 				[/codeblocks]
 			</description>