Since we no longer hardcode the `package.json` for
entry-points, a bug has appeared for `ng_package` in Ivy.
The `package.json` files are populated incorrectly with Ivy
as the flat module bundle name is not propagated from `ng_module`
to the `ng_package` rule. The rule then guesses the index file
to `index.js` and does not respect the flat module bundle shim.
PR Close#36944