Stop splitscreen from resizing to 50:50 unless it's a true launch adjacent

Adds a check for launch adjacent so that apps starting new activities within themselves don't cause a resize to 50:50. The 50:50 resize is only intended to happen for launch adjacent.

Fixes: 421272155
Flag: com.android.wm.shell.enable_flexible_two_app_split
Test: Manual
Change-Id: I0d7d1e1399be67eee7c8d8fc925702376734698e