Fix elapsed time computation in OptimisticEmitFailureHandler

[bjmi]

This change addresses the elapsed time computation in OptimisticEmitFailureHandler due to the possibility of a numerical overflow. The described behavior isn't changed from user's perspective.

Javadoc of System.nanoTime() explicitly mentions how to measure elapsed time.

To compare elapsed time against a timeout, use
if (System.nanoTime() - startTime >= timeoutNanos) ...
instead of
if (System.nanoTime() >= startTime + timeoutNanos) ...
because of the possibility of numerical overflow.

See System.nanoTime()