[CT-1236] [Feature] Convert df to pyspark DataFrame if it is koalas before writing

[dbeatty10]

Is this your first time submitting a feature request?

• I have read the expectations for open source contributors
• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing dbt-bigquery functionality, rather than a Big Idea better suited to a discussion

Describe the feature

As promised in #317, if the DataFrame to materialize as a table has type databricks.koalas.frame.DataFrame, then convert it to a pyspark.sql.dataframe.DataFrame.

Describe alternatives you've considered

Leaving it as unsupported, especially since it has a replacement since Spark 3.2

Who will this benefit?

Anyone that is using Koalas DataFrames, especially relevant for earlier versions than Spark 3.2

Are you interested in contributing this feature?

I'm your huckleberry

Anything else?

No response