Convert Commerce Product and ProfileBilling tests to use CommerceMigrateTestTrait

Postponed on #2894712: Commerce Order Tests failing.

Add assert entity tests for ProductType and ProductVariationType.

Test wasn't finished properly.

Reroll

I wonder if using the data provider pattern would make these tests easier to read and maintain. I

I would have preferred that to be a follow up. I see the advantages and like them. But one drawback I see is that ProductTypeTest and ProductVariationTest will take twice as long to run.

I also cleaned-up the test trait, because the DX of the parameter names was difficult to read.

Yes, the $expected on all the parameters is bulky. But I am so used to now that is just what I do.

I think we need to look at the product migration a little.

Whoa, odd things happening here. Some debugging and I see that after these migrations

    $this->executeMigrations([
      'd7_user_role',
      'd7_user',
      'd7_product_type',
      'd7_product',
      'd7_product_display_type',
    ]);

there aren't any products, the commerce_product table is empty.

After those are run, 'd7_product_display' is run and that creates 20 of the 84 products. The first one has an id 15, which is id 1 in the source.
]);

@heddn, thanks.