Fix custom morph map sort by

[eduPHP]

Noticed ->sortByMeta was not working properly in an application where the model has a custom morph map, so here is the fix!

Test suite all green

OK (244 tests, 1891 assertions)

New test: \Zoha\Meta\Tests\Clauses\TestCustomMorphMapOrderBy

New helper method to replace the owner_type from the fakeDataMeta array, looks a little clumsy but it is the way I managed to get a failing test without rewriting the whole seeder.

public function replaceOwnerType(string $type): void
{
    foreach ($this->fakeDataMeta as $i => $item) {
        foreach ($item as $j => $meta) {
            $this->fakeDataMeta[$i][$j]['owner_type'] = $type;
        }
    }
}

Not sure if I should push .phpunit.result.cache, so I didn't