Provide menu integration for device selection

[waliid]

Description

This PR introduces a route picker and a cast device selection in the demo app.

Changes made

Self-explanatory.

Checklist

• APIs have been properly documented (if relevant).
• The behavior works with all receivers available in the demo.
• The documentation has been updated (if relevant).
• New unit tests have been written (if relevant).
• The demo has been updated (if relevant).