expose total bytes transferred in a session

[GlenDC]

Similar to #44, it would be great if we can keep track per session on a transport level how many bytes have been written and read for a single session. This will be much more accurate then #44 as things are lot simpler and all data is going through a single point (the MITM proxy). This in contract to #44 where we try to track it individually for a single request and thus not get an accurate view and even then only because we do a lot of work to try to get to some kind of close to accurate picture.

[blakebyrnes]

glendc — Today at 5:05 PM
why? The socket has not much meaning right? As I imagine it is just the sockets that chrome opens in background (e.g. connections) to do its requests, which are probably several per session I imagine, but to the hero user they have little meaning individually, no?
then again, I can just sum the values for my purpose, so I do not mind contributing it as a per-socket thing if that's what you want, no had feelings on it :p
blakeb — Today at 5:07 PM
There are many per session, one to 4 per host endpoint. I think knowing which hosts are sending a ton of data is more useful than a generic overall number
The hosts level data is actionable
You could block certain urls based on it
blakeb — Today at 5:09 PM
That's at a hero level (db is only in hero)
blakeb — Today at 5:10 PM
In unblocked, you'll probably track in mitm-socket/index.ts 

[GlenDC]

Can be solved directly in hero. As so: ulixee/hero#225