fix(tracks) Use duration from JitsiTrack (#10304)

conference.js

             APP.store.dispatch(toggleScreenshotCaptureSummary(false));
         }
         const tracks = APP.store.getState()['features/base/tracks'];
-        const timestamp = getLocalVideoTrack(tracks)?.timestamp ?? 0;
+        const duration = getLocalVideoTrack(tracks)?.jitsiTrack.getDuration() ?? 0;
 
         // It can happen that presenter GUM is in progress while screensharing is being turned off. Here it needs to
         // wait for that GUM to be resolved in order to prevent leaking the presenter track(this.localPresenterVideo
             () => {
                 this.videoSwitchInProgress = false;
                 sendAnalytics(createScreenSharingEvent('stopped',
-                    timestamp === 0 ? null : (Date.now() / 1000) - timestamp));
+                    duration === 0 ? null : duration));
                 logger.info('Screen sharing stopped.');
             },
             error => {

react/features/base/tracks/middleware.js

         // The devices list needs to be refreshed when no initial video permissions
         // were granted and a local video track is added by umuting the video.
         if (action.track.local) {
-            action.track.timestamp = Date.now() / 1000;
             store.dispatch(getAvailableDevices());
         }