DO NOT MERGE Remove Accessability requirement from WindowUntrustedTouch.

This testclass requires Accessability service to be supported
or it can not pass. This was introduced to reduce flakiness
but can be improved in other ways. Improve setup / teardown
and make sure TestActivity does restart during the test.

Test: atest CtsWindowManagerDeviceTestCases
:android.server.wm.WindowUntrustedTouchTest

Bug: 397352498

Change-Id: I5acab9897d38b2034c5c67d19591de29c66ce066