[SPARK-13250] [SQL] Update PhysicallRDD to convert to UnsafeRow if using the vectorized scanner.

Some parts of the engine rely on UnsafeRow which the vectorized parquet scanner does not want
to produce. This add a conversion in Physical RDD. In the case where codegen is used (and the
scan is the start of the pipeline), there is no requirement to use UnsafeRow. This patch adds
update PhysicallRDD to support codegen, which eliminates the need for the UnsafeRow conversion
in all cases.

The result of these changes for TPCDS-Q19 at the 10gb sf reduces the query time from 9.5 seconds
to 6.5 seconds.

Author: Nong Li <nong@databricks.com>

Closes #11141 from nongli/spark-13250.