Automatic merge from submit-queue

scheduler: change phantom pod test from integration into unit test

This is an effort for #24440.

Why this PR?
- Integration test is hard to debug. We could model the test as a unit test similar to [TestSchedulerForgetAssumedPodAfterDelete()](https://github.com/kubernetes/kubernetes/blob/132ebb091af3b625df0ad19a5975119e800bebef/plugin/pkg/scheduler/scheduler_test.go#L173). Currently the test is testing expiring case, we can change that to delete.
- Add a test similar to TestSchedulerForgetAssumedPodAfterDelete() to test phantom pod.
- refactor scheduler tests to share the code between TestSchedulerNoPhantomPodAfterExpire() and TestSchedulerNoPhantomPodAfterDelete()
- Decouple scheduler tests from scheduler events: not to use events