Add named worker queues

[tinysec]

Summary

• expose named default, priority, and interactive worker queue APIs
• root each asynchronous action with a one-shot GCHandle until the native callback completes
• contain callback exceptions and release callback state on every completion path
• validate all three queues against the real Binary Ninja worker pool

Validation

• dotnet build -c Release --no-restore (0 warnings)
• targeted E2E: 1/1 passed
• full external E2E: 236/236 passed