Flaky ReconfigurationIntegrationSpec: small CSV source can finish before pause

### Task Summary
`ReconfigurationIntegrationSpec`'s two CSV-sourced tests use a 100-row source (`smallCsvScanOpDesc`). The run can reach COMPLETED before the `pauseWorkflow` round-trip takes effect; when it does, `PauseHandler.pauseWorkflow` finds no running regions and emits the current state (COMPLETED) rather than PAUSED, so `TestUtils.shouldReconfigure`'s `Await.result(pausedReached, 10.seconds)` times out and the test fails. The existing `Retries` mixin does not help because the race recurs on retry. Fix by using `mediumCsvScanOpDesc` (100k rows) so the run stays in flight when pause lands, matching the non-flaky sibling specs `ReconfigurationSpec` and `PauseSpec`. Surfaced on the `amber-integration` CI job (e.g. run 28017649934).
### Task Type
- [x] Test