Fix API in CaptivePortal and ConnectivityManager

 - Remove CaptivePortal constructor from SystemApi. This constructor was
   added in Q timeframe and ends up being unnecessary since
   CaptivePortal creation was refactored to ConnectivityService because
   of visibility issues on ICaptivePortal.
 - Rename getAvoidBadWifi to shouldAvoidBadWifi
 - Add permission annotation for shouldAvoidBadWifi

Test: flashed, WiFi and captive portal works
Bug: 128935314
Bug: 128935673
(clean cherry-pick of AOSP I7395d4a4db6a64398a827692aee1956c011873e5)

Change-Id: I09545c00af3519dbf141dd5951b28f49e37b3e80