Fix kubeconfig-sync issues (#2692)

- Removed `getFreePort` as its use is always a race condition. Change
  all uses of it to retrive the port after listening

- Added `getPortFrom` as a helper function to read a port from a stream

- Remove `Cluster.ownerRef` as it is outdated and no longer needed for 5.0

- Remove `Cluster.enabled`, no longer needed because of above

- Removed `Cluster.init`, moved its contents into `Cluster.constructor`
  as nothing in that function is asyncronous. Currently only being run
  on `main` as a stop gap until `renderer` gets its own version of
  `Cluster`

- Refactored `LensProxy` so as to prevent `pty.node` (a NodeJS
  extension) being included in `webpack.extension.ts`'s run

- Removed the passing around of the proxy port as that can now be
  accessed from an instance of `LensProxy`

- purge ContextHandler's cache on disconnect

Co-authored-by: Sebastian Malton <sebastian@malton.name>

src/renderer/components/layout/__test__/main-layout-header.test.tsx

@@ -7,20 +7,50 @@ import "@testing-library/jest-dom/extend-expect";
 import { MainLayoutHeader } from "../main-layout-header";
 import { Cluster } from "../../../../main/cluster";
 import { ClusterStore } from "../../../../common/cluster-store";
-
-const cluster: Cluster = new Cluster({
-  id: "foo",
-  contextName: "minikube",
-  kubeConfigPath: "minikube-config.yml",
-});
+import mockFs from "mock-fs";
 
 describe("<MainLayoutHeader />", () => {
+  let cluster: Cluster;
+
   beforeEach(() => {
+    const mockOpts = {
+      "minikube-config.yml": JSON.stringify({
+        apiVersion: "v1",
+        clusters: [{
+          name: "minikube",
+          cluster: {
+            server: "https://192.168.64.3:8443",
+          },
+        }],
+        contexts: [{
+          context: {
+            cluster: "minikube",
+            user: "minikube",
+          },
+          name: "minikube",
+        }],
+        users: [{
+          name: "minikube",
+        }],
+        kind: "Config",
+        preferences: {},
+      })
+    };
+
+    mockFs(mockOpts);
+
     ClusterStore.createInstance();
+
+    cluster = new Cluster({
+      id: "foo",
+      contextName: "minikube",
+      kubeConfigPath: "minikube-config.yml",
+    });
   });
 
   afterEach(() => {
     ClusterStore.resetInstance();
+    mockFs.restore();
   });
 
   it("renders w/o errors", () => {