Change some getCurrent/LastLocation() logic

-Change getCurrentLocation to fail faster when settings are not correct,
etc...
-Change getLastLocation() to not require a LocationRequest
-Create getLastLocationUnsafe() to allow getting a location with less
safety checks in some circumstances (such as when getting a locaiton for
the GNSS clock).

Test: manual
Change-Id: I2871352a0ef313ba4a3ce9530820a7c14cc9a5ce