Automatic merge from submit-queue
Add an integration test library and some integration tests for scheduler
**What this PR does / why we need it**:
1. Add an integration test library (utils.go) for scheduler testing.
2. Cleaned up some of the tests in scheduler_test.go with the new integration test library.
3. Add priority_test.go with a couple of examples on how to test scheduler priority function in integration tests.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
ref/ #48176
@kubernetes/sig-scheduling-pr-reviews
@davidopp @k82cn @vikaschoudhary16
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