Add an integration test to verify NUD failure due to router MAC changes.

Simulate a MAC address change scenario where the device sends broadcast
ARP request to query the default gateway's MAC address, but receives two
ARP replies, that would trigger onReachabilityFailure callback and WiFi
refreshes L3 provisioning.

Bug: 315076572
Test: atest NetworkStackIntegrationTests
Change-Id: I3f77cedb68e88ccd8ce215c16eb0b43b90256f12