For now we could get the window title from ViewRootImpl, so
we delete all obsolete code. Besides we add new string
for the tile of the pip window and split-screen divider
Bug: 210985169
Test: atest android.accessibilityservice.cts
manual test with talkback
Change-Id: Ia418b2f4175636c2109082b8daeb7b2cc1cfd845