track tool overhead

[bashbaug]

Description of Changes

This PR adds the ability to tracks, reports, and logs some types of tool overhead, such as for adding device timing events, checking device timing events, and inserting flushes or finishes after enqueue operations. This can be used to distringuish between overhead in an application and overhead in the intercept layer itself.

Because tracking tool overhead can add overhead, the "tool overhead tracking" can optionally be disabled via a control to minimize overhead, though the control is enabled by default.

Also adds a few optimizations to reduce tool overhead, such as by caching the process ID.

Testing Done

Tested with several applications, with various combinations of HostPerformanceTiming and ChromeCallLogging enabled.