Floss: Implement Pandora GATT profile (part2).

Bug: 301000123, Bug: 300942866, Bug: 300942867, Bug: 300954033, Bug: 300954035, Bug: 301000124
Test: mma packages/modules/Bluetooth && pts-bot GATT
Tag: #floss
Flag: EXEMPT floss only changes
Change-Id: I36965d425321368b6ae6d9b886c4a52924bc2d80