[Bug] Service injections doesn't work with `index` files

[chancancode]

🐞 Describe the Bug

In most other places, you can equivalently have foo.js and foo/index.js (except in controller and routes where "index" has a special meaning) and expect things to work. However, if you have app/services/foo/index.js instead of app/services/foo.js you will get an error. Seems like we should be able to make it work?

🔬 Minimal Reproduction

1. Create app/services/foo.js
2. Inject it into a component or something else
3. Observe that it works
4. Rename the service to app/services/foo/index.js
5. Observe that it doesn't work
6. Add back app/services/foo.js and re-export from the index file manually
7. Observe that it works

😕 Actual Behavior

Step 5 throws an error.

🤔 Expected Behavior

Step 5 should Just Work™.

🌍 Environment

• Ember: 3.26
• Node.js/npm: -
• OS: -
• Browser: -

[elgordino]

I've reproduced in ember-source 5.1.1 here https://github.com/elgordino/service-injection-index

[spuxx-dev]

Subscribing since I'm interested in a fix