Add onReachabilityFailure api in IIpClientCallbacks aidl.

The new API is called when neighbor reachability loss event happens
since networkstack-aidl-interfaces-V13, this CL also defines a few
associated constants representing different neighbor reachability
loss events and a stable parcelable as the parameter.

Bug: 204723906
Test: atest NetworkStackTests
Change-Id: Ie6382206de2107aa4654f0628f2f446017d7ea34