Currently remediationAction has no effect on Gatekeeper Constraints.

• Add a new field of `gatekeeperEnforcementAction`
• Default value of the field is unset and when unset, don't touch the constraint (existing behavior)
• If set, then directly set `spec.enforcementAction` in the Gatekeeper constraint
• Should be settable at the policyDefaults, policy, and manifest levels (i.e. like the `ConfigurationPolicyOptions` struct).

 Related: https://github.com/open-cluster-management-io/policy-generator-plugin/issues/155