Need to add new function - schema_of_csv(). The function should infer schema of CSV string literal. The result of the function is a schema in DDL format.
One of the use cases is passing output of schema_of_csv() to from_csv() (see
SPARK-25393). The new function should allow schema inferring from an example. Let's say csv_col is a column containing CSV string with the same schema. It should be possible to pass a CSV string with the same schema to schema_of_csv() which infers schema for the particular example.