Extract LocationProviderManager

This extracts LocationProviderManager as a completely stand-alone class,
substantially reducing the complexity in LMS, and in
LocationProviderManager. Core AOSP location code is now unit testable
for the first time, and we begin adding unit tests.

Test: extensive manual tests + presubmits
Change-Id: I0fb17ddbf91bdd26ed7855110026b3dd09612a5c