Update filter_testdata to add more reference variables

[shlyaeva]

Description

Updates filter_testdata to add more reference variables for testing diagnostic flags bitmap. The new variables:

group: TestReference {
  variables:
    int zeroes(Location) ;
        zeroes:_FillValue = -2147483643 ;
    int ones(Location) ;
        ones:_FillValue = -2147483643 ;
    int twos(Location) ;
        twos:_FillValue = -2147483643 ;
    int threes(Location) ;
        threes:_FillValue = -2147483643 ;
  data:

   zeroes = 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ;

   ones = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ;

   twos = 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 ;

   threes = 3, 3, 3, 3, 3, 3, 3, 3, 3, 3 ;

  } // group TestReference

Impact

Required for ufo PR3420, can be merged before that.

Checklist

• [x] I have performed a self-review of my own code
• [x] I have run the unit tests before creating the PR

[BenjaminRuston]

awesome @shlyaeva ,,, these are not drafts ;0)