Add two new change stream cursor stats to serverStatus output on mongoS:

• metrics.changeStreams.cursor.totalOpened (counter)
  • Cumulative number of change stream cursors opened on the router process.
  • This metric can be used to calculate change stream cursor opening rate. A constantly high rate indicates possible improper use or other problems.
• metrics.changeStreams.cursor.lifespanMicros.avg (gauge)
  • Average change stream cursor lifespan (duration in microseconds between opening and closing) on the router process.
  • Many short-lived cursors and many resumes might indicate improper use or other problems.