Issue #2157691 by damiankloip: Move some helper methods in errors.inc to an Error utility class.

core/includes/bootstrap.inc

core/includes/errors.inc

core/includes/session.inc

core/includes/update.inc

core/lib/Drupal/Core/Controller/ExceptionController.php

core/lib/Drupal/Core/Utility/Error.php

.../modules/migrate/lib/Drupal/migrate/MigrateExecutable.php

core/modules/simpletest/lib/Drupal/simpletest/TestBase.php

.../lib/Drupal/system/Tests/System/ShutdownFunctionsTest.php

...dules/system/tests/modules/system_test/system_test.module

core/tests/Drupal/Tests/Core/Utility/ErrorTest.php