Automatic merge from submit-queue (batch tested with PRs 40696, 39914, 40374)
Cleanup scheduler server with an external config class
**What this PR does / why we need it**:
Some cleanup in cmd/server so that the parts which setup scheduler configuration are stored and separately tested.
- additionally a simple unit test to check that erroneous configs return a non-nil error is included.
- it also will make sure we avoid nil panics of schedulerConfiguration is misconfigured.
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