Upgrade to phpunit 8

Add to obsolete classes PhpUnit 6.x only classes

Author: ihor-sviziev

dev/tests/static/testsuite/Magento/Test/Legacy/_files/obsolete_classes.php

@@ -4254,5 +4254,7 @@
     ['Magento\Elasticsearch\Elasticsearch5\Model\Adapter\DataMapper\ProductDataMapperProxy'],
     ['Magento\Elasticsearch\Elasticsearch5\Model\Adapter\DataMapper\ProductDataMapper'],
     ['Magento\Elasticsearch\Model\Adapter\DataMapper\DataMapperResolver'],
-    ['Magento\Elasticsearch\Model\Adapter\Container\Attribute']
+    ['Magento\Elasticsearch\Model\Adapter\Container\Attribute'],
+    ['PHPUnit_Framework_MockObject_MockObject' => 'PHPUnit\Framework\MockObject\MockObject'],
+    ['PHPUnit\Framework\BaseTestListener'],
 ];