[client/host/idd] correct frame timing attribution

Use calibrated copy-queue timestamps to separate source and effect
waits from the actual framebuffer copy.

Exclude producer readiness waits from client import timing so the
same interval is not counted in both Copy and Import.

client/transports/LGMP/lgmp.c

@@ -622,7 +622,7 @@ static void lgmp_getFrameTiming(LG_Transport * this,
       this->pendingFrame->frameSerial != frame->serial)
     return;
 
-  /* The producer writes these immediately before completing the framebuffer.
+  /* The producer writes these immediately after completing the framebuffer.
    * nextFrame can observe the header earlier, so sample them only after the
    * renderer's onFrame call has consumed the framebuffer. */
   for (unsigned i = 0;