Log image load errors (#47419)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47419

Minor improvements to `ImageExample` so we log when images fail to load. Also replaces a `Text` component with `RNTesterText` so it's legible.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D65363864

fbshipit-source-id: 6c7ce8d5af6aabfed21479c784911bdcffe4684e