Get kvm exits info for vcpu from /sys/kernel/debug/kvm/vcpu_stat.
Related openeuler kernel commits:
    bbb5023b977aa3ec08d142daa63c86e8e4da81ff
    5ae004462e253e23690b47692d514705223c0305
    167fbfb3d28c267d98064a36c95cee21cdfd2fa7
Signed-off-by: NJiajun Chen <1250062498@qq.com>

Get threads list from /proc/pid/task, and refresh data for every thread.
Display threads info below domain info.
Signed-off-by: NJiajun Chen <1250062498@qq.com>

Calculation formula of CPU usage:
cpu_time = (utime_now + stime_now) - (utime_pre + stime_pre);
CPU usage = cpu_time / time_interval;

Get utime and stime from /proc/qemupid/stat, then we can get cpu_time
by calculate variation of these value over time.
And time_interval represent cpu time interval between two data acquisition.
Signed-off-by: NJiajun Chen <1250062498@qq.com>

Read /proc/qemupid/stat file to refresh process info,
include: parent pid, userspace time, task state and etc.
According to these data, add two display itemsi to vmtop:
S: task state
P: physical processor that task is runnning on
Signed-off-by: NJiajun Chen <1250062498@qq.com>