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/renderer/frames/cluster-frame/cluster-frame.test.tsx

@@ -48,16 +48,11 @@ describe("<ClusterFrame />", () => {
 
     testUsingFakeTime("2000-01-01 12:00:00am");
 
-    cluster = new Cluster(
-      {
-        contextName: "my-cluster",
-        id: "123456",
-        kubeConfigPath: "/irrelavent",
-      },
-      {
-        clusterServerUrl: "https://localhost",
-      },
-    );
+    cluster = new Cluster({
+      contextName: "my-cluster",
+      id: "123456",
+      kubeConfigPath: "/irrelavent",
+    });
 
     di.override(hostedClusterInjectable, () => cluster);
     di.override(hostedClusterIdInjectable, () => cluster.id);