Merge branch 'dbiryukov_populate_projects_with_pipeline_variables_mr-499491' into 'master'

Introduce Ci::ProjectWithPipelineVariable model and migration

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/176022



Merged-by: Marius Bobin <mbobin@gitlab.com>
Approved-by: Marius Bobin <mbobin@gitlab.com>
Approved-by: Fabio Pitino <fpitino@gitlab.com>
Reviewed-by: Furkan Ayhan <furkanayhn@gmail.com>
Reviewed-by: Fabio Pitino <fpitino@gitlab.com>
Reviewed-by: Marius Bobin <mbobin@gitlab.com>
Co-authored-by: Dmitry Biryukov <dbiryukov@gitlab.com>