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/common/k8s-api/__tests__/api-manager.test.ts

@@ -51,8 +51,6 @@ describe("ApiManager", () => {
       contextName: "some-context-name",
       id: "some-cluster-id",
       kubeConfigPath: "/some-path-to-a-kubeconfig",
-    }, {
-      clusterServerUrl: "https://localhost:8080",
     }));
 
     apiManager = di.inject(apiManagerInjectable);

packages/core/src/common/k8s-api/__tests__/kube-api-version-detection.test.ts

@@ -43,8 +43,6 @@ describe("KubeApi", () => {
       contextName: "some-context-name",
       id: "some-cluster-id",
       kubeConfigPath: "/some-path-to-a-kubeconfig",
-    }, {
-      clusterServerUrl: "https://localhost:8080",
     }));
 
     apiManager = di.inject(apiManagerInjectable);

packages/core/src/common/k8s-api/__tests__/kube-api.test.ts

@@ -62,8 +62,6 @@ describe("createKubeApiForRemoteCluster", () => {
       contextName: "some-context-name",
       id: "some-cluster-id",
       kubeConfigPath: "/some-path-to-a-kubeconfig",
-    }, {
-      clusterServerUrl: "https://localhost:8080",
     }));
 
     fetchMock = asyncFn();
@@ -168,8 +166,6 @@ describe("KubeApi", () => {
       contextName: "some-context-name",
       id: "some-cluster-id",
       kubeConfigPath: "/some-path-to-a-kubeconfig",
-    }, {
-      clusterServerUrl: "https://localhost:8080",
     }));
 
     di.override(apiKubeInjectable, () => createKubeJsonApi({