Settings: Clean up WifiManager APIs

Promoting WifiManager#registerSoftApCallback() and
WifiManager#registerNetworkRequestMatchCallback()
to @SystemApi.

Changed method signatures to conform to API guidelines.

Also removed dead code: WifiManager#getWifiState()
never returns WifiManager#ERROR.
Remove reference to it, since it is an @hide API.

Bug: 143970861
Test: compiles
Change-Id: If4294d106f0acb5c67b5eab1f6f99bc52efc10f2

src/com/android/settings/wifi/NetworkRequestDialogActivity.java

@@ -26,12 +26,16 @@ import android.net.wifi.WifiManager.NetworkRequestMatchCallback;
 import android.net.wifi.WifiManager.NetworkRequestUserSelectionCallback;
 import android.os.Bundle;
 import android.os.Handler;
+import android.os.HandlerExecutor;
 import android.os.Message;
 import android.widget.Toast;
+
 import androidx.annotation.Nullable;
 import androidx.fragment.app.FragmentActivity;
+
 import com.android.settings.R;
 import com.android.settings.wifi.NetworkRequestErrorDialogFragment.ERROR_DIALOG_TYPE;
+
 import java.util.List;
 
 /**
@@ -115,7 +119,7 @@ public class NetworkRequestDialogActivity extends FragmentActivity implements
 
         final WifiManager wifiManager = getSystemService(WifiManager.class);
         if (wifiManager != null) {
-            wifiManager.registerNetworkRequestMatchCallback(this, mHandler);
+            wifiManager.registerNetworkRequestMatchCallback(new HandlerExecutor(mHandler), this);
         }
         // Sets time-out to stop scanning.
         mHandler.sendEmptyMessageDelayed(MESSAGE_STOP_SCAN_WIFI_LIST, DELAY_TIME_STOP_SCAN_MS);

src/com/android/settings/wifi/RequestToggleWiFiActivity.java

@@ -29,7 +29,6 @@ import android.net.wifi.WifiManager;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.util.Log;
-import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 
@@ -313,11 +312,6 @@ public class RequestToggleWiFiActivity extends AlertActivity
                         finish();
                     }
                 } break;
-
-                case WifiManager.ERROR: {
-                    Toast.makeText(activity, R.string.wifi_error, Toast.LENGTH_SHORT).show();
-                    finish();
-                } break;
             }
         }
     }

src/com/android/settings/wifi/tether/WifiTetherSoftApManager.java

@@ -36,7 +36,7 @@ public class WifiTetherSoftApManager {
     }
 
     public void registerSoftApCallback() {
-        mWifiManager.registerSoftApCallback(mSoftApCallback, new HandlerExecutor(mHandler));
+        mWifiManager.registerSoftApCallback(new HandlerExecutor(mHandler), mSoftApCallback);
     }
 
     public void unRegisterSoftApCallback() {