Implement new design of Bluetooth card

- show only up to 2 connected devices
- show the Bluetooth toggle only when it's off
- remove subtext
- when bluetooth is on but there is no connected device, show the row
  "Pair new device"

Test: robotest
Bug: 142927894
Fixes: 147892635
Change-Id: I1559fc0a4cb0b42bf447d25417ac454c29fe86c3