Implement the discovery of a network recommendation provider.

Updated the NetworkScorerAppManager to examine the list of configured
network recommendation providers and to select the first valid
provider.

As part of this update the old logic of looking for a valid network
scorer has been removed. Scorers/recommendation providers are only
selected from the configured list now. The setActiveScorer() method
has been deprecated as a result.

The NetworkScoreService has been updated to monitor the list of
potential recommendation providers and to reevaluate the binding
whenever they change. It also monitors the new setting for
NETWORK_RECOMMENDATIONS_ENABLED to connect or disconnect from the
provider as needed.

Test: runtest frameworks-services -c com.android.server.NetworkScoreServiceTest
BUG: 33158362
Change-Id: I450981261aa5355c1c91ec2e3a0a3b58cc65316b
Merged-In: I42aeb5223da794f71f7e58cb1bdf18817200cbf2