Fix some legacy-transition timing issues in split-screen

This does 2 things:

1. Leash-setup was originally made asymmetric to handle tasks
   switching between organized and non-organized; however, now the
   tasks don't do that so we can symmetrize this again.

2. TaskInfoChanged reporting was added to ensureActivityVisibility.
   This causes noise as it can repeatedly send unchanged TaskInfos to
   shell. The result is that the legacy split organizer will reposition
   its surface while it is on an animation leash. To avoid this, keep
   track of the last positions and only update it if it changes. This
   maintains a contract that as long as the task's actual position
   doesn't change (ie. during an animation), the shell won't clobber
   changes made by legacy-transition's leashing. This can be cleaned
   up once we move to shell transitions where ownership is better
   defined.

Bug: 172840531
Test: open 2 apps in split and observe no offset in launcher
Change-Id: I262e3a53b7497192e234d4a8ba215e10ed73a145