Convert forceUpdate to 'onStart' lifecycle event.

Although the AccessPointControllerImpl class is modified, there is no
longer a wifi picker in QuickSettings.

Bug: 68030053
Test: runtest --path
      frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java
Manual testing of WifiSettings cold start / resumption scenarios for UI
jank

Change-Id: Ib28edebb0acf4160cc9eda7c1620c1b4280dcdc4