Add CTS test for the capport API

The test relies on EthernetManager#setIncludeTestInterfaces to run
validation on an "ethernet" network based on a tap interface, and
simulates DHCP and HTTP servers so the device sees the capport DHCP
option, and fetches the API contents.

Bug: 156062304
Test: atest CaptivePortalApiTest
(clean cherry-pick from aosp)
Merged-In: I734dbd05c0f50b8dc4553102ab286f0d8807a7ac

Change-Id: I734dbd05c0f50b8dc4553102ab286f0d8807a7ac
2 files changed