New setting for recommendation request timeout.

Added a new global setting, NETWORK_RECOMMENDATION_REQUEST_TIMEOUT_MS,
to control the maximum amount of time a recommendation request can
take.

Updated the NetworkScoreService to monitor the value and to update
its cached copy on observed changes.

Test: runtest frameworks-services -c com.android.server.NetworkScoreServiceTest
Bug: 34060959
Change-Id: I7650ee024e53dbc856cf20d7520a6eb252c73bdf