Disable IPv6 stack when IPv6 provisioning is lost but IPv4 is still alive.

When IPv6 provisioning loss happens due to the default route has
gone, however, if IPv4 network is still provisioned, we can consider
to disable IPv6 stack and still keep the current connection without
disconnecting from wifi, applications will be able to reconnect over
IPv4 network.

Bug: 131781810
Test: atest NetworkStackTests NetworkStackNextTests
Test: atest NetworkStackIntegrationTests
Change-Id: I8f56a05b38c8387c91306c0dc2bdf4430ec3bd00