[FEA] add netstat, iostat, vfstat performance monitoring to jetson stats.

[ZhenshengLee]

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Just like what this issue #464 described, we may want to add more system performance indicator to the jtop.

After reading the official doc, there's already many indicators including cpu and memory but lacks of netio, vfs, and deviceio monitoring.

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there are many interface to get these performance indexes, like iotop, netstat and so on.

[rbonghi]

This is a cool feature! I can add from the next releases