Add a sequence_as_of column to oracle output target data

[bsweger]

Background

Because the oracle output files are not partitioned by sequence_as_of, they will be overwritten each time the hub's post-submission jobs are run (if the round_id in question is still in the 14 week window interim data window).

For normal hub operations, this is fine. However, if the target data jobs are run out of order (for example, a manual backfill run with an older nowcast_date), that would break the implicit assumption that oracle.parquet fill always reflect the most recent nowcast_date.

We decided that partitioning oracle outputs by sequence_date makes them too onerous to access. So we can't guarantee that overwriting the file won't happen, but we can add sequence_as_of information to the oracle output files as a breadcrumb.

Definition of done

• The oracle.parquet files generated by get_target_data.py will contain a sequence_as_of column

[bsweger]

I also added a tree_as_of column as part of this work, even though we didn't explicitly have that as a requirement. It aligns with our approach for the time series outputs and provides clarify for people accessing this file outside of the hub context.