Update app handle a11y to announce state descriptions

There was no indication in Talkback when certain actions had taken
place, like a window being opened, closed, minimized or changing focus.
Now there is a constant updated announcement when an app window goes
through these state changes. However they aren't always guaranteed to be
read out, since a11y focus can be stolen by other elements and sometimes
Talkback processor is throttled if alot of information updates come at
once. But this is an improvement over previous iteration, since there is
some chance of low vision users getting feedback that an event has
occured.

Bug: 398732993
Test: manually testing with talkback
Flag: com.android.window.flags.enable_desktop_app_header_state_change_announcements
Change-Id: Ie82fce2b061d950126328a21a2d20fa4d4c34b2d