Update string associated with Connected, Always On or Insecure VPNs

Previously these strings were separated with a comma, but the new design
is to separate them with a "/" and to not include always-on information
if the vpn is also insecure.

Comment thread on the strings doc: https://docs.google.com/document/d/1hjaYuGmvNzCKPOrmjixpmLLXBV8cbxgrZ3eN4KvC4E8/edit?resourcekey=0-zo7B2GVc9luQTut0o8THNA&hl=zh-TW&forcehl=1&disco=AAAAIF3eiQY
screenshot: https://screenshot.googleplex.com/BmBroUZtmUPJz9s
Test: atest -c SettingsUnitTests
Bug: 176821216

Change-Id: Ib9c273de61c9722b0beb6fba127e7481e6c64705