fix(spark): Custom annotation for SUBSTRING()

[VaggelisD]

Fixes #4002

Could not test HiveQL but the docs mention only STRING as the return type, so this PR is limited to Spark2+:

• Spark 2:

scala> spark.sql("select substring(cast('thing' as binary), 1, 2), substring('thing', 1, 2)")
res4: org.apache.spark.sql.DataFrame = [substring(CAST(thing AS BINARY), 1, 2): binary, substring(thing, 1, 2): string]

• Spark 3:

spark-sql (default)> select typeof(substring('thing', 1, 2)), typeof(substring(cast('thing' as binary), 1, 2));
string  binary

• Databricks

select typeof(substring(cast('thing' as binary), 1, 2)) as bin, typeof(substring('thing', 1, 2)) as str; 

bin	str
binary	string

Docs

Databricks SUBSTRING | HiveQL Builtin Functions

[georgesittas]

LGTM, nice 👍