Move Cluster.apiUrl to seperate injectable (#7354)

* Refactor out Cluster.apiUrl to direct reading

- Should help prevent using stale data

- Removes some uses of synchronous FS operations

Signed-off-by: Sebastian Malton <sebastian@malton.name>

* Fix type errors

Signed-off-by: Sebastian Malton <sebastian@malton.name>

* Rename helper function to better communicate intent

Signed-off-by: Sebastian Malton <sebastian@malton.name>

* Improve prometheus handler tests to override less things

Signed-off-by: Sebastian Malton <sebastian@malton.name>

---------

Signed-off-by: Sebastian Malton <sebastian@malton.name>

packages/core/src/main/cluster/update-entity-spec.test.ts

@@ -31,8 +31,6 @@ describe("update-entity-spec", () => {
       id: "some-id",
       contextName: "some-context",
       kubeConfigPath: "minikube-config.yml",
-    }, {
-      clusterServerUrl: "foo",
     });
 
     entity = new KubernetesCluster({