Pass more data through the recommendation request.

Expanding the API so it can accept the WiFi config of the currently
connected network (if any) and the set of connectable WiFi
configurations. Also renamed currentRecommendedWifiConfig to
defaultWifiConfig so the name was more representative of the
parameter's purpose and added more documentation throughout.

Test: adb shell am instrument -e class android.net.RecommendationRequestTest -w com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Test: adb shell am instrument -w com.android.networkrecommendation.tests/android.support.test.runner.AndroidJUnitRunner
Test: runtest frameworks-services -c com.android.server.NetworkScoreServiceTest
Bug: 34387385
Change-Id: I1089b70303b0396def7e6bf3737fdc67e40c9dcd