feat(carapp,media3): add voice search, transport controls, and car screen like action

[valhalla94]

What & why

Adds support for Android Auto and assistant-driven voice commands, explicit transport controls, and in-car actions:

• SimpleMediaSessionCallback:
  • Handles MEDIA_PLAY_FROM_SEARCH queries via onSetMediaItems and onAddMediaItems. Performs online search on YouTube Music and generates an auto-playing radio queue (RDAMVM<id>).
  • Added fallback in onSetMediaItems for search results not yet indexed in local database.
  • Intercepts COMMAND_PLAY_PAUSE and COMMAND_STOP in onPlayerCommandRequest and bridges them directly to mediaPlayerHandler.onPlayerEvent.
  • Implements onMediaButtonEvent to handle hardware and assistant key events (KEYCODE_MEDIA_PAUSE, KEYCODE_MEDIA_PLAY, KEYCODE_MEDIA_PLAY_PAUSE, KEYCODE_MEDIA_STOP, KEYCODE_MEDIA_NEXT, KEYCODE_MEDIA_PREVIOUS).
  • Added fallback queue resumption from Liked songs in onPlaybackResumption when no saved queue exists.
• NowPlayingCarScreen:
  • Added dynamic favorite (heart/like) toggle button in the Android Auto now-playing header alongside the queue action.
• SimpMusicCarAppService:
  • Set createHostValidator() to HostValidator.ALLOW_ALL_HOSTS_VALIDATOR to allow execution on real head units and Desktop Head Unit (DHU) without signature restrictions.
• SimpleMediaService:
  • Configured mediaSession?.setCustomLayout(commandButtonList) to export custom actions to automotive controllers.

Testing

Tested on:

• Physical Android smartphone connected to Android Auto head unit in a vehicle.
• Desktop Head Unit (DHU) emulator via ADB forwarding.

Verified scenarios:

• Voice search: "Play [Artist/Song] on SimpMusic" correctly triggers YouTube Music query and starts playback with radio queue.
• Voice transport controls: "Pause", "Play", "Next", "Previous" correctly toggle playback state.
• Car screen UI: Like button in NowPlaying header toggles favorite state and updates database.
• Cold boot resumption: launches liked songs fallback when saved playlist state is empty.