Replace usage of assertArraySubset(), that is deprecated

Had a go at the easier ones, run out of time now to do the rest,

It seems hard to get this done, as no alternative suggested.

1. Should we adopt this package to bring it back, https://github.com/rdohms/phpunit-arraysubset-asserts
2. Another good suggestion is to separate assertArraySubset() into assertAssocArraySubset($subset, $array, $strict=false) and assertIndexArraySubset($subset, $array, $order=false, $strict=false) from the comment here and Array Subset does not work as expected on indexed / flat arrays #3101, so maybe we should wrapper it as assertAssocArraySubset() to make it more clear.

3. All I have to say on this subject I have written down here.

   If you rely on assertArraySubset() and its current behaviour and want to continue to use it then, please, go ahead, take the code, and put it into an extension. Not every assertion needs to be part of PHPUnit's standard distribution.

   -- From @sebastianbergmann's comment here

   It seems @sebastianbergmann, the creator of PHPUnit does not object to using it, he just did not want to maintain it in the standard distribution.

The only complicated case is in EntityResourceTestBase:

        // Subset, not same, because we can e.g. send just the target_id for the
        // bundle in a PATCH or POST request; the response will include more
        // properties.
        $this->assertArraySubset($expected_stored_data, $modified_entity->get($field_name)->getValue(), TRUE);

Here we need to add our own recursive helper method.

Using assertContains() with string haystacks is deprecated and will not be supported in PHPUnit 9.

Unfortunately, all haystacks in the patch are arrays :p

Queued the patch against 9.0.x and it passed.

All good to me and learned from the patch, +1 to \Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase::assertEntityArraySubset()

Thanks!

Committed 09be91a and pushed to 9.1.x, cherry-picked to 9.0.x. Thanks!