[data-stats] Adds option "experimental_stats" to `tf.data.Options` which takes `tf.data.experimental.StatsOptions` object. `StatsOptions` can configure options for collecting `dataset` stats using `StatsAggregator`, and it has aggregator as an argument which attaches the given aggregator to the dataset. (this will also replace `set_stats_aggregator()` dataset transformation.)

PiperOrigin-RevId: 220230269