Add support for INTERVAL / TIMESPAN datatype in Pinot

[vvivekiyer]

The INTERVAL datatype will allow users to manipulate a period of time in years, months, days, hours, minutes, seconds, etc

Example of use:

SELECT
	now(),
	now() - INTERVAL '1 year 3 hours 20 minutes' 

Postgres reference - https://www.postgresql.org/docs/current/datatype-datetime.html