[agent][host] CPU and Memory

[at15]

I can reuse some code from Xephon-K https://github.com/xephonhq/xephon-k/issues/21, we just need to have some simple metrics so we can go ahead and prototype the UI

• [x] static CPU information, num cores, HZ, brand etc.
• [x] total CPU usage
• [x] total memory usage
• [x] per process/?thread CPU, Memory

[at15]

finished in benchhub, except the per process part ...