Set the window title in AlertDialog's AlertController

AlertDialog.Builder's setTitle() does not set the title of its
window, which TalkBack uses for announcements.

Make the behavior consistent between the AlertDialog.Builder's
setTitle and AlertDialog's setTitle, which does change the window
title.

Bug: 149755168
Test: Menu titles appear in the node tree debug info and are announced.
by TalkBack. App version info in Settings is announced.

Change-Id: I49deb98ad294538864e413c6c486b4148e06a2b6