[data-stats] Sets user given `tag` and `counter_prefix` with...

[data-stats] Sets user given `tag` and `counter_prefix` with `set_stats_aggregator`. `tag` would get prep-end with all the statistics recorded as summary and `counter_prefix` would set the prefix for the statistics recorded as counter.
Note: `counter` defaults to `\tensorflow`, and `tag` and `prefix` gets associated with the dataset (not the stats_aggregator).

PiperOrigin-RevId: 215609159