dillon1000/react

fix[devtools]: still show overlay, if getClientRects is not implemented (#35294)

Follow-up to https://github.com/facebook/react/pull/34653.

React Native doesn't implement `getClientRect`, since this is applicable
to CSS box, which is not a concept for Native (maybe yet).

I am loosening the condition that gates `showOverlay()` call to pass if
`getClientRect` is not implemented.

Conceptually, everything that is inside `react-devtools-shared/backend`
should be Host-agnostic, because both on Web and Native it is installed
inside the Host JavaScript runtime, be it main frame of the page, or RN
instance. Since overlay & highlighting logic also lives there, it should
also follow these principles.