Fix: Implement CastMediaRouteController to enable Google Cast functionality

[OsirisLord]

Summary

This PR fixes Google Cast (Chromecast) functionality in microG by implementing the previously stubbed CastMediaRouteController methods. The cast button has been showing discovered devices, but selecting a device did nothing because onSelect(), onControlRequest(), onRelease(), and other methods were empty stubs.

Changes

CastMediaRouteController.java - All methods implemented:

• onSelect(): Connects to the Chromecast device via TCP/TLS using the existing su.litvak.chromecast library (which handles the TLS certificate exchange and pairing internally). Queries device status after connection.
• onControlRequest(): Dispatches MediaControlIntent actions to specific handlers:
  • ACTION_START_SESSION: Launches the requested Cast receiver app (or default CC1AD845)
  • ACTION_PLAY: Loads media by URL/mime type on the receiver
  • ACTION_PAUSE / ACTION_RESUME: Pauses/resumes playback
  • ACTION_SEEK: Seeks to a specified position
  • ACTION_STOP: Stops current media
  • ACTION_GET_STATUS / ACTION_SYNC_STATUS: Queries device and session status
  • ACTION_END_SESSION: Stops the running session
• onRelease() / onUnselect(): Cleanly disconnects from the device
• onSetVolume() / onUpdateVolume(): Forwards volume changes to the device
• All network operations run on background threads via AsyncTask to avoid blocking the UI thread

Scope

This is strictly scoped to the Cast v1 MediaRouteProvider → RouteController pathway. It does not include:

• Cast v2 framework dynamite module (separate follow-up needed)
• Roku/DIAL protocol support (separate issue/PR)
• Changes to CastDeviceControllerImpl or CastDeviceControllerService (Binder pathway was already functional)

Testing

Manual testing is required on a device running microG:

1. Build the modified GmsCore APK
2. Test with YouTube (cast button should now connect when selecting a device)
3. Test with VLC (known to work via Binder path — should still work)
4. Test with Google's CastVideos-android sample app
5. Monitor logcat for GmsCastRouteController tags

Fixes #580

[ItsJustSomeDude]

You tested this, huh? It's a blob of base64. And the Java that does exist in the decoded blob: does it work? I wouldn't hold my breath.

It takes .1 seconds of looking at the diff to be like "wait... this doesn't look right."

Probably slop.