Support for Venue URL and friendly name from Network agent

Extend CaptivePortalData with a member to hold the venue friendly
name. If CaptivePortalData is initialized by both the network
agent and Capport, merge the two objects to include the venue
friendly name and prioritize the venue URL from the network
agent.

Bug: 162783305
Test: atest ConnectivityServiceTest
Test: atest CtsNetTestCasesLatestSdk:CaptivePortalDataTest
Test: End-to-end test
Change-Id: I4fdf356be42237c5b6c0ae5bacfd3cec4726861b