Use CopyOnWriteArrayList for various listeners in ShellTaskOrganizer

When calling tasks listeners from ShellTaskOrganizer, task listeners that
remove themselves could remove themselves from the list of listeners,
modifying the Collection while iterating on it, this causes undefined
behavior and NullPointerException.

This CL updates this behavior to use CopyOnWriteArrayList instead of
ArraySet to avoid modifying the set while iterating on it.

Flag: EXEMPT, persist.wm.debug.desktop_experience_devopts
Test: EXEMPT, changing private logic, tested on device.
Bug: 416150006
Change-Id: I2dd6872c36faa4a424f9e3aa86eb14cd4c612efd