Capture meeting start and video recording start time vs stage time

[JamesPHoughton]

Currently, we can sync videos with each other based on the time that the recording starts (or the time the call starts? need to check). However, we also may want to synchronize the video with the stage timer. The meeting and recording may take a second or two to start, so if we care about precise coordination (ie, reactions to surprising stimuli) we need to measure either the stage start time with the same (or coordinated) clock as the video recording (which is coming from daily's servers) or we need to register the stage elapsed time when the meeting and recording start.