The regexp Postgres functions **Reporter**: [Mike Seddon](https://issues.apache.org/jira/browse/ARROW-11654) / @seddonm1 <sub>**Note**: *This issue was originally created as [ARROW-11654](https://issues.apache.org/jira/browse/ARROW-11654). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*</sub>