Ensure feature flags are set on Staging, before Production

To make sure testing on staging is reflective of what users will experience on production we should expand feature flags to check that staging and production are staying in sync.

• When we set a featureflag on Production, we should do an extra check to make sure the same feature flag is set on Staging. If it isn't set, we can fail and allow an override flag to bypass the failure.
• When we diable a featureflag on staging, we should check if the same feature flag is enabled in Production. If it is set, fail and allow the same override flag to bypass the failure.

This is a corrective action for incident gitlab-com/gl-infra/production#5367 (closed)