[Bug]: Move Fakes to a test module

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Is there a StackOverflow question about this issue?

- [X] I have searched StackOverflow

### What happened?

`core/data/src/main/java/com/google/samples/apps/nowinandroid/core/data/repository/fake` has a bunch of fakes

### Relevant logcat output

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Start by inspecting core/data/src/main/java/com/google/samples/apps/nowinandroid/core/data/repository/fake and the surrounding module layout to determine which fakes are test-only. Done means the fakes reside in an appropriate test module and are no longer part of the production source set; run the relevant data tests afterward.

Written by the indexing model from the issue text.