Implement metadata provider changes in the privacy api

[ewallah]

failure: provider_testcase::test_userdata_provider_implements_userlist with data set "metadatacontext_user" ('metadatacontext_user', 'metadatacontext_user\privacy\provider')
Failed asserting that false is true.
vendor/bin/phpunit "provider_testcase" privacy/tests/provider_test.php

failure: provider_testcase::test_table_coverage
The following tables with user fields must be covered with metadata providers:

• ranking_points (userid)

vendor/bin/phpunit "provider_testcase" privacy/tests/provider_test.php