[WifiTrackerLib] Display "Available via..." summary for suggestions

Suggestion networks should display "Available via..." in their summary,
followed by the carrier name if it is a carrier suggested network, or
the name of the app that suggested it.

Bug: 153029289
Test: manual visual verification of wifi picker with suggestions
installed

Change-Id: I620e412d0daa631376e6ef455d77049d1aa954f2
2 files changed