nvme_test: mirror changes from nvme emulator to support multiple submission queues

[gurasinghMS]

nvme spec requires multiple submission queues to be able to target a single completion queue. The main nvme emulator has already implemented this logic in commit 722d203 on the main branch.
Changes from that commit need to be applied EXACTLY over to the nvme_test emulator as well. Since the files are named the same and the code has barely diverged, this should be a pretty straightforward task.