[Handoff][1/N] Fix Parceling of App Icon

Actually parcel the app icon properly - the previous approach didn't encode the class name in the parcel, so it couldn't be marshalled

Test: Manual testing
Bug: 400970610
Flag: android.companion.enable_task_continuity
Change-Id: Icc437c022d0063063a0f31aa8c96531ce0cdc714