Implement core_privacy for tool_assignmentupgrade

Testing can be completed by running the attached testwithmanager.php script (see ----------- MDL-61571 ----------- for the original script location) in the Moodle root folder. Make sure you've purged the caches (php admin/cli/purge_caches.php), before running testwithmanager.php. Check that tool_assignmentupgrade plugin is compliant Check that   tool_assignmentupgrade plugin is metadata provider. You should receive a script output like: Testing the compliant plugins:   .......   == tool_assignmentupgrade (tool_assignmentupgrade\privacy\provider) == Found 1 items of metadata Nothing to export.