Implement Set Operators for Time Types

[chaitan94]

• +: Union of the time values
• *: Intersection of the time values
• -: Difference of the time values

We can override the respective operators in both C++ and Python
Invalid operations should throw accordingly

Todo Checklist

• TimestampSet, TimestampSet
  • Union
  • Intersection
  • Difference
• Period, Period
  • Union
  • Intersection
  • Difference
• PeriodSet, PeriodSet
  • Union
  • Intersection
  • Difference
• PeriodSet, Period
  • Union
  • Intersection
  • Difference

Sample MobilityDB queries for reference/test cases

mobilitydb=# select period '[2020-01-01, 2020-01-10]';
                      period                      
--------------------------------------------------
 [2020-01-01 00:00:00+00, 2020-01-10 00:00:00+00]
(1 row)

mobilitydb=# select period '[2020-01-01, 2020-01-10]' + '[2020-01-08, 2020-01-10]';
                      ?column?                      
----------------------------------------------------
 {[2020-01-01 00:00:00+00, 2020-01-10 00:00:00+00]}
(1 row)

mobilitydb=# select period '[2020-01-01, 2020-01-10]' + '[2020-01-08, 2020-01-12]';
                      ?column?                      
----------------------------------------------------
 {[2020-01-01 00:00:00+00, 2020-01-12 00:00:00+00]}
(1 row)

mobilitydb=# select period '[2020-01-01, 2020-01-10]' + '[2020-01-18, 2020-01-20]';
                                               ?column?                                               
------------------------------------------------------------------------------------------------------
 {[2020-01-01 00:00:00+00, 2020-01-10 00:00:00+00], [2020-01-18 00:00:00+00, 2020-01-20 00:00:00+00]}
(1 row)