Rename getAllNetworkStateSnapshot which should be pluralized

Address API review feedback, ConnectivityManager#getAllNetworkStateSnapshot
should be pluralized so rename the method to getAllNetworkStateSnapshots

(cherry picked from ag/14221105)
Bug: 183972554
Test: make, FrameworksNetTests
      FrameworksServicesTests
Merged-In: Ic18d17d05984fa2466c962c7843c0ef7183ce77c
Change-Id: Ic18d17d05984fa2466c962c7843c0ef7183ce77c