floss: reject media profile connections for second device

This CL adds some checks to reject multiple BT audio devices, by
disconnecting audio profile connections when there are other active
connections.

Bug: 379971553
Tag: #floss
Test: mmm packages/modules/Bluetooth
Flag: EXEMPT, Floss-only change
Change-Id: Ida7a5e23ef05fa63c33bb2e75d073d638b95ee2c