[Handoff][2/N] Handle Fallback URIs when launching Handoff Activities

* Handle multiple activities when performing Handoff
* Launch fallback URIs if Handoff activities cannot launch


Test: Updated unit tests
Bug: 400970610
Flag: android.companion.enable_task_continuity
Change-Id: Iff687379a0ae14c9a619f4576de3b02a1dbde0cc