mgr/nvmeof: introduce nvmeof module and create .nvmeof rbd pool on orch nvmeof apply

mgr/nvmeof: introduce nvmeof module and create .nvmeof rbd pool on orch nvmeof apply

Introduce a new NVMe-oF mgr module and which create the pool
used for storing NVMe-related metadata ceph orch nvmeof apply command.
This removes the need for users to manually create and configure the
metadata pool before using the NVMe-oF functionality, simplifying
setup and reducing the chance of misconfiguration.
Signed-off-by: Tomer Haskalovitch <tomer.haska@ibm.com>