Create Screenshot Detection APIs

This is a followup on ag/19854404

The APIs are used on a per Activity granularity, a client can register
their callback via: `registerScreenCaptureCallback(mExecutor, mCallback);` on Activity

The activity token is used to communiate from the client side to the
ActivityTaskManager and ActivityRecord on the server side. The WMS will receieve a notification when the hardware chord for screenshots is triggered by the user, it would then find all activites that have visible windows and trigger the callbacks registered on all of them.
for more details, see go/screenshot-detection-dd

Bug: 245115438
Test:  CTS tests && Manual
Change-Id: I27bf708ac86187f066971b1b01c5b308f78a01b3