feat(phpunit): consider data providers in children classes as valid test entrypoints

[simPod]

I expected this would break some tests but it does not 🤷🏾‍♀️

abstract class TestCaseBase extends TestCase
{
    abstract public static function providerTest(): array;

    #[DataProvider('providerTest')]
    public function testFoo(string|null $phpValue, string|null $serialized): void
    {
    }
}

final class SomeExtendingTest extends TestCaseBase
{
    public static function providerTest(): array
    {
        return [];
    }
}

Data providers in children classes are also valid entrypoints.

[janedbal]

Thanks!