Extension API: Create System APIs to allow OEM module to override WiFi

scorer in AOSP

Create WiFi scorer interface and score change callback interface in WifiManager; Define register and unregister methods for WiFi scorer.

Test: atest android.net.wifi
Bug: 135573686, 122133502, 136312816, 135572156

Change-Id: Ib51d877a463d1f69b31b9743917ea1b3590a30f7
Signed-off-by: Mingguang Xu <mingguangxu@google.com>