In "Analyze Query Plans" mode, collect service call stack traces in DarkConsole

Summary: Ref T13106. When profiling service queries, there's no convenient way to easily get a sense of why a query was issued. Add a mode to collect traces for each query to make this more clear. This is rough, but works well enough to be useful.

Test Plan: Clicked "Analyze Query Plans", got stack traces for each service call.

Maniphest Tasks: T13106

Differential Revision: https://secure.phabricator.com/D19221