Create public API ScanResult.getSecurityTypes()

Public API ScanResult.getSecurityTypes() should be created for Settings
and WifiTrackerLib to reference the security types corresponding to a
scan result without implementing their own copies of helper methods
already implemented in ScanResultUtil.

Bug: 187755981
Test: atest FrameworksWifiApiTests
Change-Id: If9eb3c12897943f13cb0937d5ae4ce383668c2be
4 files changed