[outdated] ZO_ComboBox sort order

[merlight]

Reviving because:

1. sort by "name" is still hardcoded in ComboBoxSortHelper
2. incorrect is-defined-tests of sortOrder (which may be ZO_SORT_ORDER_DOWN == false) are still there, only moved to ZO_ComboBox_Base:UpdateItems and ZO_ComboBox_Base:SetSortOrder
3. found another such incorrect test in ZO_SortHeaderGroup:OnHeaderClicked
   

   function ZO_SortHeaderGroup:OnHeaderClicked(header, suppressCallbacks, forceReselect)
       if self:IsEnabled() then
           local resetSortDir = false
           if forceReselect or not self:IsCurrentSelectedHeader(header) then
               self:DeselectHeader()
               resetSortDir = true
           end
    
           -- this is wrong, initialDirection == false should be taken as valid value
           self.sortDirection = resetSortDir and header.initialDirection or not self.sortDirection
   ...

   
   fixed:
   

   function ZO_SortHeaderGroup:OnHeaderClicked(header, suppressCallbacks, forceReselect)
       if self:IsEnabled() then
           if forceReselect or not self:IsCurrentSelectedHeader(header) then
               self:DeselectHeader()
               self.sortDirection = header.initialDirection
           else
               self.sortDirection = not self.sortDirection
           end
   ...