Enable launching captive portal directly

Whenever a user has connected to a captive portal network, split the
ConnectedAccessPointPreference to allow directly signing into the
captive portal or modifying the network's settings. When in any other
network state, use the old behavior of a single tappable preference that
takes the user to settings.

Bug: 63929546
Bug: 68031656
Test: make RunSettingsRoboTests
Test: manual by connecting to Captive Portal and normal WiFi networks.

Change-Id: I444202a12138d90c94bda94945c121c8c0810536
(cherry picked from commit 7577624d)