Remove media_route_control_frame in media_route_controller_dialog

This UI is never used in the code (always stay hidden with no support).
This is legacy code and can be removed.

Also remove some other unused functions and variables.

Test: manual, open Quick Settings, click on Cast tile and check dialog
Bug: 395947047
Flag: NONE clean up legacy code

Change-Id: I7f4e409a471ea552454972568b54e0016cf0a153