[CORE] vmm_loadbal: Improve crude load balancer

This patch improves our existing crude load balancer making it
more sensible and also keeping the simplicity.

The improved crude load balancer is very simple and lazy. It will
balance VCPUs based on host CPU utilization. It does not consider
the VCPU nature (i.e. IO-bound or CPU-bound) and rather treats all
ready VCPUs equally when balancing. For newly created VCPUs, it
will try to provide host CPU with least number of READY, RUNNING,
and PAUSED VCPUs.

Folks aiming at developing their own application-centric or HW-centric
load balancer can use the updated crude load balancer as reference.

Signed-off-by: Anup Patel <anup@brainfault.org>