[3/N][Requesting Handoff from App] Create OutboundHandoffRequestController

This is part of a stack of changes to send requests for Handoff to connected associations and process response messages into actual app launches

This change adds a controller to pass incoming requests to hand off a task to a remote device from the API.

Test: Added unit tests
Bug: 400970610
Flag: android.companion.enable_task_continuity
Change-Id: Ie8a22d7fd93f766ed98be58e503e8349e0fda8e6