Add support for targeting ZoneEgress in MeshTimeout

[Automaat]

Description

We have designed how we want to target zone proxies in MADR. We now need to implement possibility to configure ZoneEgress as stated in MADR. API should look like:

spec:
  targetRef:
    kind: ZoneEgress
  rules:
    - targetRef:
        kind: MeshExternalService
        name: my-external-service
      default:  ...

In targetRef inside rules we should be able to select:

• Mesh
• MeshService
• MeshMultizoneService
• MeshExternalService