Merge branch 'package_reg_testid_migration' into 'master'

Migrate Package Registry and Pages selectors to use testid

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138816



Merged-by: Jacques Erasmus <jerasmus@gitlab.com>
Approved-by: Jay McCure <jmccure@gitlab.com>
Approved-by: Scott de Jonge <sdejonge@gitlab.com>
Approved-by: Jacques Erasmus <jerasmus@gitlab.com>
Co-authored-by: Will Meek <wmeek@gitlab.com>