Default Carrier app for traffic mitigation

- have the basic function working, support traffic mitigation and
  captive portal login
- support carrier customization, OEM could configure a list of carrier
  actions to act upon certain signals
- unit test

Test: Manual test with live sim card & runtest --path
frameworks/base/packages/CarrierDefaultApp
Bug: 30958215

Change-Id: Ie99be3b95e8a1dd60fc51bef703836478fbde09d