As a rapid board owner I would like to be able to have a column constraint for "Issues, excluding Sub-Tasks"

Testing Notes

Q: What happens in the case with an issue that has a subtask not captured by the filter?
A: Nothing - the count is for parent issues and not sub-tasks, so the count will not be affected.

Q: Test to see this works with Stories Swimlane config, as well as Queries.
A: Still works, though it is less clear what the issue count refers to given that you do not see the parent issue in the column it is in.

Q: What about negative numbers?
A: They continue to not be allowed - same input controls for constraints as before.

Q: Is this customizable for individual constraints, or globally for all constraints?
A: For the whole board, not individual columns

Q: What if the last parent is removed from that column but it's subtasks remain?
A: The count drops to zero.

Q: What happens if there is no subtask issuetype?
A: Nothing - the count should not be affected by issues which do not exist

Q: What happens when there are quick filters active that filter out parent issues? What happens when there are quick filters active that filter out sub-task issues?
A: The count should still display the appropriate number of issues - so if column constraint excludes sub tasks then filtering out parents should set all visible counts to 0.