Make new task follow source task root

For current split UX, we want new task launched by old task can
stay in split. To achieve this, add a rule if source task's root
task is created by organizer then use it as root task of new task.

Bug: 202740040
Test: manual
Test: pass existing tests
Change-Id: Ibcbf3c4f78607a9ca44eee29c4c078daf1c46402