Testing: More e2e tests for Keptn Scheduler

[RealAnna]

Technical Details

Current scheduler test only assert the following specs:

1. If annotated for keptn-scheduler, a new Pod should stay pending if no workload instance is available ✓
2. If annotated for keptn-scheduler, a new Pod should be scheduled when workload instance pre-evaluation checks are done ✓
3. If NOT annotated for keptn-scheduler, a new Pod should be immediately scheduled ✓

Acceptance Criteria

• Add tests for points 1, 2, and 3 but using labels instead of annotations
• If annotated for keptn-scheduler, a new Pod should not be scheduled when workload instance pre-evaluation checks fail

DoD

• Scheduler behavior is tested also against label usage
• Scheduler behavior is tested also against pre-eval failure