Allow ADB to be enabled by default via a config overlay

This is useful for developers that are testing and troubleshooting boot issues
and adb ends up being disabled by default once the system kicks in.  This should
only be used for testing and removed once a device is deemed stable and able to
boot.

Change-Id: Ib17d4e10ec68640ce55a91d5b1067d3d37eeec9d
Disable debug music transport control

Change-Id: I5b458899b0ce5157980ee2fe406af2e2191ee0e2
Fix Google backup/restore

Change-Id: Idd5f63caf58742fc7a52d42e8e64731387983876
Enable Dessert Cake dream

Change-Id: I987154631bab920698ee1d1c3e1d04d80b397ad7