virtio_fs: add sysfs entries for queue information

virtio_fs: add sysfs entries for queue information

Introduce sysfs entries to provide visibility to the multiple queues
used by the Virtio FS device. This enhancement allows users to query
information about these queues.

Specifically, add two sysfs entries:
1. Queue name: Provides the name of each queue (e.g. hiprio/requests.8).
2. CPU list: Shows the list of CPUs that can process requests for each
queue.

The CPU list feature is inspired by similar functionality in the block
MQ layer, which provides analogous sysfs entries for block devices.

These new sysfs entries will improve observability and aid in debugging
and performance tuning of Virtio FS devices.

Reviewed-by: Idan Zach <izach@nvidia.com>
Reviewed-by: Shai Malin <smalin@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Message-Id: <20240825130716.9506-2-mgurtovoy@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>