* Use consistent naming for unstable_testing entry point
* Exclude the testing build from non-experimental builds except at FB
* FB builds shouldn't contribute to whether we include the npm files
* Exclude exports fields if we delete the files entry
* Move test to no longer be internal so we can test against the build
* Update the bundle artifact names since they've now changed
* Gate import since it doesn't exist
This change adds a new "react-dom/unstable_testing" entry point but I believe its contents will exactly match "react-dom/index" for the stable build. (The experimental build will have the added new selector APIs.)