Support moving task to an activated split stage in a specific position

Split screen might has been activated when other components like
Launcher or PIP task organizer invoking enterSplitScreen API. This makes
sure the indicated task will be moved to the correct split side after
split screen activated.

Fix: 206745122
Test: atest WMShellUnitTests
Test: manual check expanding PIP task to split behavior
Change-Id: I6210846c6f4443727e93fcf313539a34c0f3298a