RFE- Namespace serial number is assigned by default while creation, We should allow custom serial number for namespaces

- We see namespace getting the same serial number under each subsystems- which again leads to confusion when we have multi subsystem enviornments - when having single client/initiator and discover multi subsystems

- However, From practical stand point, its good to have unique serial number for namespace within and across subsystems to ensure proper identification, management and avoid conflicts or confusions in multi-subsystems enviornments

Below snippet- container 3 subsystems and serial number under each subsystems is identical with other subsystems

[root@ceph-ci-nvme-preethi-78viqm-node7 cephuser]# nvme list
Node Generic SN Model Namespace Usage Format FW Rev

/dev/nvme2n1 /dev/ng2n1 1 SPDK bdev Controller 1 107.37 GB / 107.37 GB 4 KiB + 0 B 23.01
/dev/nvme1n3 /dev/ng1n3 1 SPDK bdev Controller 3 107.37 GB / 107.37 GB 4 KiB + 0 B 23.01
/dev/nvme1n2 /dev/ng1n2 1 SPDK bdev Controller 2 10.74 GB / 10.74 GB 4 KiB + 0 B 23.01
/dev/nvme1n1 /dev/ng1n1 1 SPDK bdev Controller 1 107.37 GB / 107.37 GB 4 KiB + 0 B 23.01
/dev/nvme0n2 /dev/ng0n2 1 SPDK bdev Controller 2 10.74 GB / 10.74 GB 4 KiB + 0 B 23.01
/dev/nvme0n1 /dev/ng0n1 1 SPDK bdev Controller 1 10.74 GB / 10.74 GB 4 KiB + 0 B 23.01
[root@ceph-ci-nvme-preethi-78viqm-node7 cephuser]#

The issue names no files or tests; begin by tracing the Python namespace-creation entry point and where the default serial number is assigned. Reproduce the multi-subsystem case shown by the `nvme list` output, then verify behavior for a caller-supplied namespace serial number and uniqueness across namespaces.

Written by the indexing model from the issue text.