* Support Listener in Property Override
Add support for patching `Listener` resources via the builtin
`property-override` extension.
Refactor existing listener patch code in `BasicEnvoyExtender` to
simplify addition of resource support.
* Support ClusterLoadAssignment in Property Override
Add support for patching `ClusterLoadAssignment` resources via the
builtin `property-override` extension.
Michael Zalimeni