Expose netstat-like information

[wkozaczuk]

It would be nice to have OSv present netstat-like information. Actually, on the Spirent fork there is a version of it that adds new capabilities to the libtools and httpserver-api modules (see SpirentOrion@ba29876). But I suggest that instead of enhancing libtools and httpserver-api, instead, we expose this information as a psuedo-file (is there something like this on Linux?) which is described in issue #1205.