SUREFIRE-1044 TestNG execution based on XmlClass

SUREFIRE-1044  Goes back to the state of TestNG execution as it was in surefire-plugin 2.15.
Now method org.testng.TestNG.run during execution contains 1-XmlTestSuite with 1-XmlTest as many  XmlClass as we have  test classes
Since  TESTNG-476 TestNG 6.1 order of test execution should be preserved