Per-World GWB Isolation

[eanticev]

Summary

Implements per-world isolation for Gameplay Work Balancer by transforming the global singleton to a world-specific manager architecture. Key changes:

• Added TMap of world-specific managers in UGWBSubsystem
• Updated static APIs to route through world context
• Ensured independent work tracking and scheduling per world
• Maintained backwards compatibility with existing APIs

Detailed Changes

• Refactored UGWBSubsystem to manage multiple UGWBManager instances
• Added world-aware manager retrieval methods
• Updated static work scheduling to use world context
• Implemented cleanup for stale world references

Testing

• Added multi-world isolation test cases
• Verified independent work tracking across worlds
• Ensured proper manager lifecycle management

Migration

Existing code can be updated by replacing:

// Old
UGWBSubsystem* Subsystem = GEngine->GetEngineSubsystem<UGWBSubsystem>();
UGWBManager* Manager = Subsystem->GetManager();

// New
UGWBManager* Manager = Subsystem->GetManagerForWorld(GetWorld());

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