Summary:
The current way the Jest preset work requires the different files to be in `<rootDir>/node_modules/react-native`. This is not necessarily true - especially in monorepoes.
If we instead do `require.resolve`, we do not need to do `rootDir` replacement in Jest.
Having a JS file as preset has been supported since Jest 23.0.0: https://github.com/facebook/jest/pull/6185
Changelog:
----------
[General] [Fixed] - use `require.resolve` in `jest-preset`
Pull Request resolved: https://github.com/facebook/react-native/pull/22972
Differential Revision: D13662758
Pulled By: hramos
fbshipit-source-id: ca79b5b89d9d05c6fe639b0d88619858e8d05da7
