Enable advanced Picture in Picture and Control Center integration for the chapter-supporting player

[defagos]

Description

This PR enables advanced Picture in Picture and Control Center integration for the chapter-supporting player. This was initially omitted but felt awkward when navigating SRG SSR content from a demo user perspective.

Changes made

• Enable advanced PiP for the player supporting chapters.
• Enable Control Center integration for the player supporting chapters.
• Revisit the implementation to have correct animations during PiP restoration. Instead of manual state registration it suffices to split the view into subviews with local Player observation.
• Track the player view.
• Make highlighted chapters slightly more prominent.

Checklist

• [x] APIs have been properly documented (if relevant).
• [x] The documentation has been updated (if relevant).
• [x] New unit tests have been written (if relevant).
• [x] The demo has been updated (if relevant).