DO NOT MERGE Add developer menu to select max number of connected audio devices

The new developer option modifies the system property
"persist.bluetooth.maxconnectedaudiodevices"; it allows testing
multiple connected devices for A2DP, AVRCP, HFP.

Bug: 71603731
Test: Robolectric test
Change-Id: If8c2c26ad4c9a2b7458a2d16a0c29d5f9b4df5c7