Update xgboost models and metrics

[leewyang]

Updated xgboost models/metrics for "combined", "databricks-aws", "databricks-azure", "dataproc" with latest datasets and fixes.
Updated metrics for "emr" and "onprem" to include split=val rows.

Changes:

• Fixed split_nds function to avoid including nds-h queries.
• Include split=val when computing feature metrics.

[parthosa]

Thanks @leewyang.

[cindyyuanjiang]

Thanks @leewyang!