Add ci_akeyless_secret feature flag
Ref: https://gitlab.com/gitlab-org/gitlab/-/issues/475179
What does this MR do and why?
This MR creates ci_akeyless_secret
feature flag with some boilerplate code to unblock a contributor.
It will be used by a community contribution in order to fully implement the rest of the feature in !147283 (closed).
Edited by Max Orefice