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
Change-Id: I734dbd05c0f50b8dc4553102ab286f0d8807a7ac
diff --git a/tests/cts/net/Android.bp b/tests/cts/net/Android.bp
index 93a6d91..82b7413 100644
--- a/tests/cts/net/Android.bp
+++ b/tests/cts/net/Android.bp
@@ -39,6 +39,7 @@
 
     static_libs: [
         "FrameworksNetCommonTests",
+        "TestNetworkStackLib",
         "core-tests-support",
         "compatibility-device-util-axt",
         "cts-net-utils",