Add product guided tour overlay

[ilyasfoo]

Issue description

In WordPress.com product guided tour, some elements are highlighted despite being under overlay:

WPCOM	Jurassic Ninja

To reproduce

1. In an ecommerce plan site, go to Homescreen > Add your products
2. Click on any product type
3. Observe the guided tour highlight issue

Acceptance criteria

1. Elements not focused by the guided tour shouldn't be highlighted