ConfigFromEnv loads `simqueue` config from environment.

MultipleWorkers creates n workers that are rate limited by limit.

ErrLaggingBlock is returned by ProcessFunc if item should be processed by block that current node doesn't yet have.

ErrProcessScheduleNextBlock is returned by ProcessFunc if item should be retried on the next block.

ErrProcessUnrecoverable is returned by ProcessFunc if item should not be retried.

ErrProcessWorkerError is returned by ProcessFunc if item should be retried on the same block by a different worker.

RedisQueueConfig is the configuration for RedisQueue.