As discussed in the PR, those fields can go down, so they cannot be advertised
as type COUNTER. But the type is shared for the whole family, so we need to
create a new family to keep the other ones as COUNTER and add the new ones
as GAUGE.
kernel/sched/cputime.c says above get_cpu_idle_time_us() and get_cpu_iowait_time_us():
> Note that this is partially broken due to the counter of iowait tasks that
> can be remotely updated without any synchronization. Therefore it is possible
> to observe backward values within two consecutive reads.
steal is apparently also unreliable because it is reported by the hyperviser.
So let's be cautious and report it as gauge too.