Wait starting window finished in syncInputTransactions

This CL is attempt to fix the test flakiness happens when invoking
tapOnDisplayCenter on the test activity but the starting window
is still exists.

Use ActivityRecord#hasStartingWindow to check all running activities
to ensure input window transations will wait until the starting
window has finished animating.

Bug: 191996095
Test: atest MultiDisplaySystemDecorationTests#\
      testDisplayPolicyImeHideImeNoSystemDecorations --iterations 100
Change-Id: Ie9ca44a7b4c972fc1393d9ce55a5982a2b62dac7