Add a hidden API to inject location.

New API allows system clients with LOCATION_HARDWARE and
ACCESS_FINE_LOCATION to inject a location to the Location Manager.  This
is useful in products like Auto, where the location needs to be cached
across reboots.

Bug: b/64125396
Test: Foll. were tested:
1. location can be injected when lastLocation is not available
2. location cannot be injected when lastLocation is already available
Also, tested location availability on different devices for sanity.
Change-Id: I1fd060caafed0431074ae64439ac52e99e0d6032