Perfomance : changed batch submit and consumer get logic

[AmineDiro]

After running benchmarks on the current implementation, the scheduling algorithm changed for the following:

• Batch submit : submit all items to 1 random queue > batch submit evenly distributes work on queues
• Consumers : on start a consumer will get an assigned queue by the queuepool, the queuepool cycles through the _queues

This changes are a result of running several benchmark and tests.

We aim to have as much performance measured in : high throughput, low submit_time and work_time.