WifiNetworkScoreCache: Use @hide INetworkScoreCache

This version of WifiNetworkScoreCache extends the @hide AIDL callback.
This will not be a part of the mainline module and will be used by
settings/setupwizard.

Bug: 144487252
Test: Compiles
Test: Device boots up & connects to wifi networks.
Change-Id: I3bf1525642329d4cc55830985ab5fb89ff651912