Change the switcher to switch LE audio mode with broadcast

Change the previous toggle design to list option for broadcast feature.
The new toggle change is only applied as broadcast feature enabled whcih
is behind a feature flag.

Bug: 273153850
Test: make RunSettingsRoboTests ROBOTEST_FILTER=BluetoothLeAudioPreferenceControllerTest
Change-Id: Ic2ea10d9d9529a2d413525c1b660f8fbac371502