Allow changing the mock location returned by GNSS HAL

This CL introduces a new lshal debug command for GNSS HAL
  location [lat=..] [lon=..] [ele=..] that allows changing
the mock location provided by GNSS HAL to clients

This can be used manually to configure a single mock location,
or in a scripted scenario to, e.g., supply a set of locations
from a GPX file to simulate a moving device

Bug: None
Test: set different locations via command line to Cuttlefish device, e.g.
$ adb shell lshal debug android.hardware.gnss@2.1::IGnss/default location lat=46.6317 lon=-114.0789
Change-Id: I7217c59f66f1ee7f5a9bd3f3dd3af7be4b43c024