Fix launch flow when one app in an app pair is paused

This CL changes the error handling logic in ItemClickHandler to continue with app pair launch when only one app in an app pair is paused. It also changes AppPairIconGraphic so that the disabled state of the app pair is drawn modularly (if only one app is paused, only one app will appear visually paused).

Bug: 330795643
Flag: ACONFIG com.android.wm.shell.enable_app_pairs TRUNKFOOD
Test: Manual
Change-Id: Ieaf0120cced07b6ac0f3eb07c75b66666a8dcc85