Introduce Tasks migrated from old codebase

gems/gitlab-backup-cli/lib/gitlab/backup/cli.rb

gems/gitlab-backup-cli/lib/gitlab/backup/cli/tasks.rb

...itlab-backup-cli/lib/gitlab/backup/cli/tasks/artifacts.rb

gems/gitlab-backup-cli/lib/gitlab/backup/cli/tasks/builds.rb

...backup-cli/lib/gitlab/backup/cli/tasks/ci_secure_files.rb

...gitlab-backup-cli/lib/gitlab/backup/cli/tasks/database.rb

gems/gitlab-backup-cli/lib/gitlab/backup/cli/tasks/lfs.rb

...gitlab-backup-cli/lib/gitlab/backup/cli/tasks/packages.rb

gems/gitlab-backup-cli/lib/gitlab/backup/cli/tasks/pages.rb

...gitlab-backup-cli/lib/gitlab/backup/cli/tasks/registry.rb

...ab-backup-cli/lib/gitlab/backup/cli/tasks/repositories.rb

gems/gitlab-backup-cli/lib/gitlab/backup/cli/tasks/task.rb

...backup-cli/lib/gitlab/backup/cli/tasks/terraform_state.rb

.../gitlab-backup-cli/lib/gitlab/backup/cli/tasks/uploads.rb

...tlab-backup-cli/spec/gitlab/backup/cli/tasks/task_spec.rb