MultiHal 2.0 - proxying api calls helper methods

Create getSubHalForSensorHandle method which will get the proper subhal
pointer by getting the subhal list index from the first byte of the
sensor handle. Create the zeroOutFirstByte static helper method that
will return a version of the sensor handle without the first byte when
passed a handle.

Test: Tested compilation.
Bug: 136511617
Change-Id: I7d07003e1903aa1d8abaf904b778248c7b352653