Automatic merge from submit-queue (batch tested with PRs 42940, 42906, 42970, 42848)
Move node and event observer helpers to e2e/common
**What this PR does / why we need it**:
Moves existing test helper functions in OIR e2e tests to `test/e2e/common`. These functions wrap informers to help test writers to observe events instead of long-polling for status updates.
For usage examples, see `test/e2e/opaque_resource.go`.
cc @kubernetes/sig-scheduling-misc
**Release note**:
```release-note
NONE
```