With EvictionsInBackground alpha feature getting implemented through https://github.com/kubernetes-sigs/descheduler/pull/1466 the KDO needs to allow to enable it for existing profiles. The goal here is to extend the list of customizations with a new `EvictionsInBackground` field. An alternative is to expose a new FeatureGates list with a predefined set of FGs. If a specific feature gate gets enabled the operator may set OpenShift specific defaults (which are a subject to change).

TODO

• KDO can enable EvictionsInBackground feature
• descheduler is synced with upstream and EvictionsInBackground feature is carried under o/descheduler as a downstream patch
• deploy KDO and test the eviction in background with kubevirt installed
• allow to limit the number of evictions per a descheduling run