Try solving flaky unit test by switch to use different implementation of setImmediate (#5655)

Signed-off-by: Janne Savolainen <janne.savolainen@live.fi>

src/common/test-utils/flush-promises.ts

@@ -2,4 +2,6 @@
  * Copyright (c) OpenLens Authors. All rights reserved.
  * Licensed under MIT License. See LICENSE in root directory for more information.
  */
-export const flushPromises = () => new Promise(resolve => setTimeout(resolve, 0));
+import { setImmediate } from "timers";
+
+export const flushPromises = () => new Promise(setImmediate);

src/jest.setup.ts

@@ -6,6 +6,7 @@
 import fetchMock from "jest-fetch-mock";
 import configurePackages from "./common/configure-packages";
 import { configure } from "mobx";
+import { setImmediate } from "timers";
 
 // setup default configuration for external npm-packages
 configurePackages();
@@ -22,7 +23,7 @@ fetchMock.enableMocks();
 // Mock __non_webpack_require__ for tests
 globalThis.__non_webpack_require__ = jest.fn();
 
-global.setImmediate = global.setImmediate ?? (<TArgs extends any[]>(callback: (...args: TArgs) => void, ...args: TArgs) => setTimeout(() => callback(...args), 0));
+global.setImmediate = setImmediate;
 
 global.fail = ((error = "Test failed without explicit error") => {
   console.error(error);