Allow ATV Keychord to turn on/off talkback

Bug: 74307653
Test: manual - tested on elfin

1) Pair emote app to Android TV
2) use keychord (Dpad_down + back) to trigger on/off talkback

(currently, emote app is the only remote that can pair with ATV and
send/trigger 2 keyevents simultaneously to actually trigger the keychord)

---

Talkback was consuming keyevents between interceptKeyEventBeforeQueueing
and interceptKeyEventBeforeDispatching, so if we move the logic that
schedules the toggling of the accessibility feature to the
"...BeforeQueueing" method we can turn off talkback appropriately.

The original CL was located here: ag/4466951. This CL will be CPed back
to pi-tv-dev.

Change-Id: I2c4e532c09d57a1a3cf093cfb7e3d5557f6b9929