Remove all C++ Telemetry Accumulation calls.

This creates a number of stubs and leaves some surrounding code that may be irrelevant (eg. recorded time stamps, status variables).
Stub resolution/removal should be a follow-up to this.

xpcom/threads/HangMonitor.cpp

@@ -249,8 +249,6 @@ NotifyActivity(ActivityType aActivityType)
 
   // If we have UI activity we should reset the timer and report it
   if (aActivityType == kUIActivity) {
-    mozilla::Telemetry::Accumulate(mozilla::Telemetry::EVENTLOOP_UI_ACTIVITY_EXP_MS,
-                                     cumulativeUILagMS);
     cumulativeUILagMS = 0;
   }