Replace findNodeHandle with reading _componentViewTag

[gaearon]

Summary

Partially addresses #6719.

This is better because it doesn't enter the traversal codepath inside React. The findNodeHandle calculation inside the Animated.View itself is not so bad because it's short circuited inside for native refs (at least with View). Whereas passing a class instance like here always triggers the slower path in React. Regardless, it's already computed so why compute again?

Test plan

I've added console logs in our app to verify whether animatedComponent._componentViewTag === findNodeHandle(animatedComponent) and it always turned out true in the cases I hit.

Not sure if there any cases where those could be different.

[tjzel]

I recall there was an issue that if a component doesn't have its own native representation (it wraps a View for example) then we need to re-obtain the tag in some cases (when the underlying View changes). Not sure if it applies here however.

[piaskowyk]

I really appreciate that you reported the issue and submitted a PR! Thanks for your time 🙏. I wanted to address other areas where we use the findNode handler, so I've created another PR that builds upon yours - #6736