[SPARK-3065][SQL] Timestamp support in the parser

If you have a table with TIMESTAMP column, that column can't be used in WHERE clause properly - it is not evaluated properly. [More](https://issues.apache.org/jira/browse/SPARK-3173)

- [x] modify SqlParser so it supports casting to TIMESTAMP (workaround for item 2)
- [ ] modify Comparable expression evaluation so the the explicit casting is not necessary