Deprecate register* for UDFs in SQLContext and Catalog in PySpark
Seems we allow many other ways to register UDFs in SQL statements. Some are in SQLContext and some are in Catalog.
These are also inconsistent with Java / Scala APIs. Seems we better deprecating them and put the logics into UDFRegistration (spark.udf.register*).
Please see this discussion too - https://github.com/apache/spark/pull/20217#issuecomment-357134926.