Make Information Elements (IE) of a scan result available as a public API.

Bug: 137835398
Test: atest FrameworksWifiTests
Test: attach to upstream hotspot device by selecting the sanned
      ssid from wifi settings, then check the OUI, vendor specific
      type fileds of IEs from the logcat.

Change-Id: If3b9906c75033f51bd35fcf054154125719ea958