[Handoff][2/N] Update Local Task Store when Remote Task Updates

This is part of a series of changes to add Handoff to AOSP.

This change processes incoming RemoteTaskUpdatedMessages from remote devices, updating the local store of remote tasks to match the update messages.

Test: Added Unit Tests
Bug: 400970610
Flag: android.companion.enable_task_continuity
Change-Id: I323c5aa0881e4d8e9920ccf17a7fb78f7f8517ba