test: Adapt in_flight_syncpoint_during_scheduling for next-gen mode

Description

The integration test in_flight_syncpoint_during_scheduling needs to be updated to be compatible with next-gen mode.

Context

This test currently assumes behavior in the existing scheduling flow. In next-gen mode, scheduling behavior and timing can differ, which may make the current assertions or setup incompatible.

Steps to Reproduce

1. Run the integration test suite with next-gen mode enabled.
2. Execute the in_flight_syncpoint_during_scheduling case.
3. Observe incompatibility/failure under next-gen mode.

Proposed Solution

• Review test assumptions that are tied to legacy scheduling behavior.
• Refactor setup/assertions so the test validates expected behavior in next-gen mode.
• Keep behavior checks deterministic across both modes if dual-mode support is required.

Additional Information

• Test case: in_flight_syncpoint_during_scheduling
• Area: integration tests / scheduling / syncpoint