[FEA] Support python API execution for power script

[jihoonson]

Is your feature request related to a problem? Please describe.
The power run scripts currently only supports running SQLs. I wish the scripts would support running python function as well. This will be useful as some queries are not easy to express with SQL.

Describe the solution you'd like
Instead of SQLs in the query file, I would have python function in it. The below is an example.

# start query 1 in stream 0

def test(spark):
    spark.read.table("store_sales").groupBy("ss_item_sk").count()

# end query 1 in stream 0

Describe alternatives you've considered

I'm not sure what alternatives might exist, but would welcome any suggestions.