Performance profiling: Consider adding net/http/pprof endpoint

[seryl]

Feature Request

Add pprof endpoint so we can get better detail into where and why the router's spending it's time.

go-torch should help a lot with visualization if we put this in place.

Likely we'll want to get this in place if we want to hit top-end limits for number of routing rules or time per routing rule.

There's some examples of getting graphviz output here.

Like this:

[timoreimann]

We've had a few performance questions / issues on this area already, so I think having a proper pprof endpoint would be super valuable. I've used it myself on other projects with great success.

It should come with a switch to enable/disable on a per-need basis.