net/mlx5: Refactor vport QoS to use scheduling node structure

Refactor the vport QoS structure by moving group membership and
scheduling details into the `mlx5_esw_sched_node` structure.

This change consolidates the vport into the rate hierarchy by unifying
the handling of different types of scheduling element nodes.

In addition, add a direct reference to the mlx5_vport within the
mlx5_esw_sched_node structure, to ensure that the vport is easily
accessible when a scheduling node is associated with a vport.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>