Use generators for large data providers (#6508)

|      Q       |   A
|------------- | -----------
| Type         | improvement
| Fixed issues | N/A

#### Summary

While merging 3.9.x I found myself debugging PHPStan errors in the
humongous array shape that is the `dataExpandListParameters` data
provider. I'd like to use a generator function instead which should give
us more precise static analysis results in the future.

These are mostly whitespace changes. GitHub's default diff view is not
very helpful, I'm afraid. 🙈