[30763] Use stable sort for manual position

Only moved items are being sorted, to avoid sorting the entire page when
that is not yet necessary. This is a design decision to ensure only the
minimum number of positions are being assigned and helps when sorting a
restricted set of work packages from a bigger set.

To avoid having ambiguous sort results, ensure a second sort parameter
by ID.

https://community.openproject.com/wp/30763

app/models/queries/work_packages/columns/manual_sorting_column.rb

@@ -34,7 +34,7 @@ class Queries::WorkPackages::Columns::ManualSortingColumn < Queries::WorkPackage
   def initialize
     super :manual_sorting,
           default_order: 'asc',
-          sortable: "ordered_work_packages.position NULLS LAST"
+          sortable: "#{OrderedWorkPackage.table_name}.position NULLS LAST, #{WorkPackage.table_name}.id"
   end
 
   def sortable_join_statement(query)