Moved emulated User HAL capabilities into a library.

So it can be used by other Vehicle HAL implementations.

Test: adb shell lshal debug android.hardware.automotive.vehicle@2.0::IVehicle/default --user-hal
Test: adb shell lshal debug android.hardware.automotive.vehicle@2.0::IVehicle/default --help
Test: m -j android.hardware.automotive.vehicle@2.0-emulated-user-hal-lib

Bug: 150167241
Bug: 150409377

Merged-In: I2d0c5039c3b994dfe10d3b411f6d502bebe7cca0
Change-Id: I2d0c5039c3b994dfe10d3b411f6d502bebe7cca0