Code review comment for ~ogayot/curtin:nvme-o-tcp-storageconfig

As we are adjusting the config format, we want to update doc/topics/storage.rst as well with the changes to add the new storage command.

As we're early days in terms of nvme-stas support, I suggest you mark that documentation experimental similar to how ZFS things are marked.

Please either include that doc change in this MP, or land it first, so that we don't forget to do the doc update.

More of a review later.