HDMICEC: Dynamic soundbar mode feature

This feature gives users of STB/OTT devices with built-in or connected speakers the possibility to use it as a proper soundbar for the audio of the TV or other connected devices, supporting the main CEC functionalities for soundbars.

Bug: 237275185
Test: make && atest com.android.server.hdmi
Change-Id: I919eb3c75a89599135d3bb6bf52f0a4488e51dcf