Add a view that emulates the SYS_CALENDAR.CALENDAR table from Teradata

[Hackerpilot]

This will help people migrating code from Teradata to BigQuery. Placing this in views/migration/teradata to mimic the structure of the UDF directories. So far there seems to be no test infrastructure for views, so let me know what, if anything, needs to be done to test this. So far this has just been manually tested.

[Hackerpilot]

Pushed a new version that fixes a few cases. Tested with this:

select * from 
(select 4, weekday_of_month,
  4, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-10-24')
union all
(select 3, weekday_of_month,
  3, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-10-18')
union all
(select 5, weekday_of_month,
  4, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-10-29')
union all
(select 1,  weekday_of_month,
  0, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-10-1')
union all
(select 1, weekday_of_month,
  1, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-5-1')
  union all
(select 1, weekday_of_month,
  0, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-9-1')
  union all
(select 1, weekday_of_month,
  0, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-9-2')
  union all
(select 1, weekday_of_month,
  0, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-9-3')
    union all
(select 2, weekday_of_month,
  1, week_of_month, calendar_date
  from dummy.CALENDAR
  where calendar_date = '2022-9-9');