Wait for ANRd process to be killed before starting next test

We must wait for the ANRd process to be fully killed. If we simply click
on "close" button on the dialog, this is not sufficient. The system
would still be processing ANR and trying to kill the process. This
killing action will therefore impact the next 'am start' command. The
second activity will never be launched.

In this CL, add a wait by polling the 'ApplicationExitInfo' lists before
and after the 'close' button is clicked.

Bug: 196111779
Test: atest InputTests:AnrTest
Change-Id: I35e8f4ba302d0f1ed4a03be2257541a4e9a638f4