Add setScreenUnlockedFunctions method to UsbManager

The screen unlocked functions save effort on setting
the usb config during each connection. These
functions persist between connections and between
boots. When the screen is unlocked and these
functions are set, the current functions will
be automatically set to the screen unlocked functions.

Also added svc command for this so it can be
used and tested while the UI is worked on.

Bug: 62876645
Test: svc usb setScreenUnlockedFunctions mtp
Test: Test functions with locking, unlocking, and
disconnecting, with no lockscreen, swipe, and pattern

Change-Id: Ia05e095917166d25398c4d310b02971e3a1bb12a