introduce a new annotation release.openshift.io/feature-gates that accepts a comma separated list of feature gates which must be enabled to consider a manifest for inclusion within the cluster, optionally preceeded by a - to negate that (ie don't include me if this gate is enabled).

The PR adds a feature gate informer to the core operator which keeps a synchronised list of enabled feature gates. This is then passed through to sync workers, added to the sync worker status, and finally passed into the library-go manifest inclusion/exclusion code for decisions on whether the manifest should/shouldn't be included.

https://github.com/openshift/cluster-version-operator/pull/1273