btif: av: minor refractory to have a more comprehended state update

Update the btif_av interface to report state updates more comprehensively.
With this patch, every connection attempt will consist of a CONNECTING +
CONNECTED/DISCONNECTED. And all voluntary disconnection will have a
DISCONNECTING emitted.

Minor syntax fixes.

BUG: 240781725
Tag: #floss
Test: ./build.py
Test: emerge-${BOARD} floss
Test: gd/cert/run
Change-Id: I01c1fc995380b7448860e918f27ed7355e4e5fae