[ts-transformers] Improve position of static properties and add blank line

[aomarks]

Input

class MyElement extends LitElement {
  static styles = css`...`;

  @property()
  foo;
}

Current output

class MyElement extends LitElement {
  static properties = {
    foo: {},
  }
  static styles = css`...`;
}

Desired output

class MyElement extends LitElement {
  static styles = css`...`;

  static properties = {
    foo: {},
  }
}

Specifically, we should:

• When creating a new static properties field, put it below the last existing static field, instead of at the top of the class.
• Add a blank-line placeholder to new static properties fields.