Merge Istio.spec.components and Istio.spec.values

The configuration of an Istio component such as Pilot is split across two Istio spec fields: components and values. As a user, I want to configure a component in one place.

We should merge the two fields into a new field. It should probably not be called values, since this is a Helm-related concept and the fact that the operator uses Helm underneath is an implementation detail and so it should be hidden from the API (i.e. the Istio CRD).