Fix integer overflow in round-robin load balancing

[dkropachev]

Summary

• Fix potential ArrayIndexOutOfBoundsException from AtomicInteger overflow in round-robin selection
• Ensure safe index calculation even after billions of requests

Changes

• Replace Math.abs() with bitwise AND operation to handle Integer.MIN_VALUE case
• Use (counter & Integer.MAX_VALUE) to ensure non-negative index
• Maintain round-robin distribution behavior while preventing crashes

Test plan

• Verify compilation passes
• Test round-robin distribution still works correctly
• Verify no crashes when counter approaches Integer.MAX_VALUE
• Confirm behavior with Integer.MIN_VALUE overflow case