Add metrics for how long sidecar commands take

[phillco]

Could be useful for figuring out what levels of performance we're getting, since @JohnEfford found HTTP to be a bit slower.

Should be easy enough to log these out with a statsd client and if the user has an agent installed, it will pick them up.

[JohnEfford]

To be clear I don't think HTTP is slower, I don't know as I've not managed to get sockets working in windows :). My point was that I was Visual Studio (from now on I'll call it Heavy to differentiate from VS code) was adding 500ms to an action which VS Code was completing on average of 90-110ms, from HTTP request start, to HTTP request finish. A proxy (Fiddler) was showing that between Heavy start of HTTP request and VS code receiving the Http request was where the 500ms was occurring which indicates a 'my code' problem. In the screen shot below you can see the request took over 2 seconds (first column red underscore) but the majority of that is taken by the client (Heavy) getting the request to the server (VS code), highlighted in yellow.

Having said that any extra diagnostic tracing we add would be good.