Implement and integrate BatchCursorInterceptorSubscriber to wait for BatchCursor creation or to catch exceptions during aggregate operation, allowing us to uncomment and stabilize reactive streams tests affected by race conditions.

Background:

Investigations into race conditions during BatchCursor creation have led to an approach using BatchCursorInterceptorSubscriber and project reactor debugging tools, as seen in this commit: 9f469a62.

Acceptance Criteria:

• BatchCursorInterceptorSubscriber is fully integrated into the test suite.
• Tests previously disabled due to race conditions are uncommented and pass successfully