[Handoff] Add recents to permissions

Add the "recents" flag to Handoff's permissions, to guarantee the "recents" app has access to these APIs. The permissions are still restricted to system apps.

Flag: android.companion.enable_task_continuity
Bug: 400970610
API-Coverage-Bug: 419601871
Test: Built - CTS tests to come
Change-Id: I8e5cb33e2589d336275fc1ae8f1b0d8b2a5cf9f9