Eliminate race conditions in UID-based network filtering.

The previous code retrieved information from the legacy tracker multiple
times for each user query, leading to race conditions where the info
could've changed between the calls.

Refactors the handling of legacy data types in ConnectivityService and
unifies call paths so that APIs that deal with legacy data types
(NetworkInfo and int/networkType) and newer types (such as Network) go
through common code paths, using NetworkState to hold all the necessary
data pieces. This enables follow-on bug fixes to getActiveNetworkInfo().

The changes are limited to public "query" APIs (those that retrieve some
network information or the other). More details about the specific
changes and their rationale can be found in the code review thread.

Bug: 17460017
Change-Id: I656ee7eddf2b8cace5627036452bb5748043406c