Remove the double lists in WifiTracker.

This CL completes the final removal of the double handler, double list,
pending notification complexity that was introduced ag/1396615 as a
'fix' to improper API implementation of the AccessPointListener
callback. The implementation erroneously refetched the entire
WifiTracker list and then performed its own sorting everytime an
individual AccessPoint was updated, instead of waiting for WifiTracker's
WifiListener.onAccessPointsChanged (plural) method instead.

Those changes have now been reverted, and the underlying SetupWizard
code has changed since then such that it does not need to be modified to
prevent regressions.

Bug: 37674366
Test: 1. runtest --path
    frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java
2. runtest --path
    frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/AccessPointTest.java
3. Manual testing of WifiSettings for visual jank
4. Startup and manual inspection of SetupWizard Wifi Picker.

Change-Id: Ia4079859a7a892983ecf55ba8eab13d20120ff99