Add onHandoffActivityDataRequested

Add a flow to retrieve HandoffActivityData from Activity

Test: CTS Tests (https://googleplex-android-review.git.corp.google.com/c/platform/cts/+/33126285)
Flag: android.companion.enable_task_continuity
Bug: 400970610

Change-Id: If71ba67c37ac938e90071d3a5320a81f4bc506ae