[NetworkSuggestion] Allow app to set subId for the suggestion

SubId will be used to identify which SIM/subscription to use for this
suggestion. Same network with different SubIds will be consider
different suggestions.
Also add a system API in WifiConfiguration to help data calculation for
different SIM.

Bug: 169275787
Test: atest android.net.wifi

Change-Id: I093c0661e28cc2df5e97391342101e8ecc331a0f
diff --git a/wifi/api/system-current.txt b/wifi/api/system-current.txt
index bf7003c..98cb849 100644
--- a/wifi/api/system-current.txt
+++ b/wifi/api/system-current.txt
@@ -350,6 +350,7 @@
     field @Deprecated public int numScorerOverrideAndSwitchedNetwork;
     field @Deprecated public boolean requirePmf;
     field @Deprecated public boolean shared;
+    field @Deprecated public int subscriptionId;
     field @Deprecated public boolean useExternalScores;
   }