Various GNSS cleanups

-Remove GNSS disable on idle behavior. This breaks the contract of
location providers and seems likely to increase power usage by forcing
more network location usage in some circumstances. Power save modes
are already handled at a higher level, the GNSS location provider
should not need to care about them.
-Remove some unnecessary thread trampolining.
-Reorganize vars to better conform to standard ordering practices
(statics first, etc).
-Prevent double reporting of network locations to GNSS HAL.
-Prevent mock locations from being reported to the HAL.
-Switch to listener alarms instead of pending intent alarms.

Test: presubmits
Change-Id: I8c526f32b1dbcdac419d1d7644fc2e511b0f9b5c