Remove unnecessary operations
Remove unnecessary operations

- Old code that tracked rendered nodes. The code to track them was
  removed, but the ivar remained.
- Setting the rendered tree to a new VirtualDOM::Element was
  unnecessary. virtualDom.patch modifies the element in place.
- Using an attr_reader on VirtualDOM::Element was awkward because
  element.element is a weird expression to write. Instead, if we want to
  use the native element, we just use `to_n`.

clearwater-rb/clearwater,clearwater-rb/clearwater,elia/clearwater,elia/clearwater