percpu_xmit: unpin the Tx worker

Pinned threads were hard to control in terms of load balancing -
leave it to a load balancer as it should be.

The main benefit of having a Tx-worker per-CPU was to minimize the number of
IPIs but after Gleb's patch that minimizes them globaly this patch hardly
improves it.

So, in order to simplify the code and to exclude the functionality (load balancing)
duplication this patch reverts the most of the 6589babdc752d46daa8203c7fa313ac9f678f736
patch.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
dynamic_thread_priority: collect the CPU idle stats from all CPUs and not only from the local one

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
virtio::net::rxq: Use dynamic priority

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
dynamic_thread_priority: print thread name

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
percpu_xmit: Use more agressive dynamic prio thresholds (10, 20) -> (5, 10)

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>