Put allow_composite_identities_to_run_pipelines behind ff

Igor Drozdovrequested to merge
id-put-ci-behind-feature-flag into master

What does this MR do and why?

Put allow_composite_identities_to_run_pipelines functionality behind a feature flag

Related issue: https://gitlab.com/gitlab-org/gitlab/-/issues/512509+

Edited by Igor Drozdov

Merge request reports