tests: automatically create cascade persist permutations

[nikophil]

fixes #597

This PR introduces a way to automatically create all permutations for "cascade persist" relationships.

By using a combination of the trait WithEntityRelationShip, and the attribute UsingRelationShips, a data provider is automatically created with all possible combinations of the "cascade persist" and "standard" associations.

ex:

final class EntityRelationshipTest extends KernelTestCase
{
    use WithEntityRelationShip, Factories, ResetDatabase;

    // a matrix with all relationships will be created. Here, for example, there will be 4 permutations:
    // [`Contact::$category` => "cascade", `Category::$contacts` => "cascade"]
    // [`Contact::$category` => "standard", `Category::$contacts` => "cascade"]
    // [`Contact::$category` => "cascade", `Category::$contacts` => "standard"]
    // [`Contact::$category` => "standard", `Category::$contacts` => "standard"]
    #[UsingRelationShips(Contact::class, ['category'])]
    #[UsingRelationShips(Category::class, ['contacts'])]
    /**
     * @test
     * @dataProvider provideCascadeRelationshipsCombination
     */
    public function many_to_one(): void
    {
        // add some test which used `Contact::$category` and `Category::$contacts`
    }
}

If we're OK on this implementation, I think I can remove all StandardXXX and CascadeXXX classes!

Here are some thoughts about this work:

• We must add the data provider on each method using the attribute UsingRelationShips. I don't think it is possible to automatically add it, but I've added a check which enforces to add the provider if the attribute is used
• It is currently not possible to have another data provider. But for now, the tests about "orm relationships" do not use data providers, so it's good enough
• the trait WithEntityRelationShip MUST be before Factories trait. I have to find a way to enforce that. It is a problem of order in the @before hooks and this is why I decided to propose this change in PHPUnit
• I do think we should test ALL these permutations (I mean, the full matrix, with full cases), we may find some weird edge cases

[nikophil]

I need to add some tests for this stuff as well