[WifiInfo] API to get the current connection security type

Added API in WifiInfo to get the current connection security type
to allow Settings to display the true security type of a
connection.
Added a hidden API to allow the framework to set it after a
successful connection, and unset it when disconnecting.

Bug: 183015441
Test: atest WifiInfoTest ClientModeImplTest
Change-Id: I6ce54d8fa57fa275b98636099befd89b322d5069
5 files changed