Add additional preference items to WifiSettings for configuring Wi-Fi.

Removed the gear icon that links to ConfigureWifiSettings activity,
and added links to ConfigureWifiSettings and SavedAccessPointSettings.
Included these links in the wifi disabled screen.

Also refactored code to have dividers between wifi list and other settings, and
changed refresh menu item to a button.

Bug: 34518148
Bug: 33110624
Test: Manual inspection
Change-Id: Ie40935f553faea59b7a76fc050d970d431cef5ad