There were two issues:
- we did not find VDom roots inside shadow DOM
- we incorrectly relied on DOM's `contain` method to determine if
VDom's rendered node belongs to requested scope.
Fixes#10123
This patch adds support for the `react` selector engine that allows
selecting DOM elements based on the component name.
> **NOTE**: in case of multi-root components (React.Fragment), `react`
engine will select all root DOM elements.
> **NOTE**: `react` engine supports react v15+.
References #7189
