Move flush from global to test util

Also rename to waitEventLoop() and remove polymer dependency. Cases
where callback or synchronous version were used were rewritten to
promises.

Release-Notes: skip
Change-Id: I3e480d3d91db73df509a6b2da2c9b22fb94fe07b
diff --git a/polygerrit-ui/app/services/scheduler/max-in-flight-scheduler_test.ts b/polygerrit-ui/app/services/scheduler/max-in-flight-scheduler_test.ts
index 53d92ca..0f24eda 100644
--- a/polygerrit-ui/app/services/scheduler/max-in-flight-scheduler_test.ts
+++ b/polygerrit-ui/app/services/scheduler/max-in-flight-scheduler_test.ts
@@ -3,8 +3,8 @@
  * Copyright 2022 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import '../../test/common-test-setup-karma.js';
-import {assertFails} from '../../test/test-utils.js';
+import '../../test/common-test-setup-karma';
+import {assertFails, waitEventLoop} from '../../test/test-utils';
 import {Scheduler} from './scheduler';
 import {MaxInFlightScheduler} from './max-in-flight-scheduler';
 import {FakeScheduler} from './fake-scheduler';
@@ -67,7 +67,7 @@
     assert.equal(fakeScheduler.scheduled.length, 2);
     fakeScheduler.resolve();
     assert.equal(fakeScheduler.scheduled.length, 1);
-    await flush();
+    await waitEventLoop();
     assert.equal(fakeScheduler.scheduled.length, 2);
   });
 
@@ -78,7 +78,7 @@
     assert.equal(fakeScheduler.scheduled.length, 2);
     fakeScheduler.reject(new Error('Fake Error'));
     assert.equal(fakeScheduler.scheduled.length, 1);
-    await flush();
+    await waitEventLoop();
     assert.equal(fakeScheduler.scheduled.length, 2);
   });
 
@@ -89,7 +89,7 @@
     }
     for (let i = 0; i < 3; ++i) {
       fakeScheduler.resolve();
-      await flush();
+      await waitEventLoop();
     }
     const res = await Promise.all(promises);
     assert.deepEqual(res, [0, 1, 2]);