-- The previous implementation of the maxRuntime would require us to wait until all of the work was completed within a shard, which can be a substantial amount of work in the case of a locus walker with 16kb shards.
-- This implementation ensures that we exit from the traversal very soon after the max runtime is exceeded, without completely all of our work within the shard. This is done by updating all of the traversal engines to return false for hasNext() in the nano scheduled input provider. So as soon as the timeout is exceeeded, we stop generating additional data to process, and we only have to wait until the currently executing data processing unit (locus, read, active region) completes.
-- In order to implement this timeout efficiently at this fine scale, the progress meter now lives in the genome analysis engine, and the exceedsTimeout() call in the engine looks at a periodically updated runtime variable in the meter. This variable contains the elapsed runtime of the engine, but is updated by the progress meter daemon thread so that the engine doesn't call System.nanotime() in each cycle of the engine, which would be very expense. Instead we basically wait for the daemon to update this variable, and so our precision of timing out is limited by the update frequency of the daemon, which is on the order of every few hundred milliseconds, totally fine for a timeout.
-- Added integration tests to ensure that subshard timeouts are working properly
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