Draft: Implement -i init.sql feature of SparkSqlOperator

Spark SQL CLI supports a feature that enables developers to use an initialization SQL file that is executed before the actual SQL script gets executed.

This MR implements this feature so that we can configure our SparkSqlOperator instances to use it. For now we want to make it an option, however in the future we might come up with a SQL script containing a library of commonly used MACROs, and enable that by default for all SparkSqlOperator instances.

Closes T426111