Deprecate `mongodb.poll.interval.sec` and add `mongodb.poll.interval.ms`.

There is currently an option for MongoDB called mongodb.poll.interval.sec. This option does not align with the temporal unit of milliseconds like similar options and should be changed. The new option mongodb.poll.interval.ms should have precedence moving forward but the old option if exists should remain deprecated. The now deprecated option also never was described in the connector docs.