#13783 moved the service mirror permissions on Links from a Role to a ClusterRole as a side-effect, and this change reverts that by refactoring the Links API to allow consuming a namespace-scoped API more easily.
- We introduce in our `k8s.API` type a field `L5dClient` alongside the broad `Client` one, which is constructed via the new function `NewL5dNamespacedAPI()`.
- In the service-mirror `main.go` we use that constructor to acquire `linksAPI`, which is used to configure the informer for handling Link events in this file.
- `linksAPI` is also passed down to instantiations of `RemoteClusterServiceWatcher`, where it's used for the direct kube-apiserver calls and for retrieving a Lister.