Clean up updateAccessPoints.

Remove obsolete logic, refactor for efficiency and readability. No
longer make redundant, duplicate IPCs.

Bug: b/68030053
Test: runtest --path
frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java

Change-Id: I1a1077c1adaacbd759521451a994a7655befdf58