fix(policy): set an informative field manager on patches

When the policy controller patches a status, it sets the field manager to be
that of the Kind of resource being managed. Per the Kubernetes documentation,
this field should describe the controller that is making the change:

> Managers identify distinct workflows that are modifying the object (especially
> useful on conflicts!), and can be specified through the fieldManager query
> parameter as part of a modifying request. When you Apply to a resource, the
> fieldManager parameter is required. For other updates, the API server infers a
> field manager identity from the "User-Agent:" HTTP header (if present).
>
> When you use the kubectl tool to perform a Server-Side Apply operation,
> kubectl sets the manager identity to "kubectl" by default.

This commit sets the field manager to "linkerd.io/policy-controller", as is used
in status values.

policy-controller/k8s/status/src/index.rs

@@ -313,7 +313,7 @@ impl Controller {
     {
         tracing::trace!(?patch);
         let api = k8s_core_api::Api::<K>::namespaced(self.client.clone(), namespace);
-        let patch_params = k8s_core_api::PatchParams::apply(&K::group(&Default::default()));
+        let patch_params = k8s_core_api::PatchParams::apply(POLICY_CONTROLLER_NAME);
         let start = time::Instant::now();
         let result = time::timeout(
             self.patch_timeout,