Remove multiple media player support for cars.

Some cars won't work properly if AVRCP target lists
multiple media players so we gate this feature behind
a system property, while keeping the improvements made to
browsing and addressed player.

Bug: 394035701
Bug: 382419933
Bug: 393059901
Bug: 381719439
Bug: 379039786
Bug: 352279986
Bug: 338156685
Flag: com.android.bluetooth.flags.set_addressed_player
Test: atest BluetoothInstrumentationTests
Change-Id: I982a524d924fc7dbeaac3407cfaeafdb8d114949