[Wi-Fi] Hide the Advanced Option after expanding the advanced option fields.

To align with other advanced option behaviors in other Settings items, hide the Advanced Option button after the hidden advanced options are show, which also solve the a11y issue.

Bug: 146908469
Test: Add test case getVisibility_whenAdvancedOptionClicked_shouldBeGone
to verify View is Gone.
Change-Id: I11b2f9b250a7d50d32b8c05207498f4cf14feb41

tests/robotests/src/com/android/settings/wifi/WifiConfigControllerTest.java

@@ -549,4 +549,13 @@ public class WifiConfigControllerTest {
         assertThat(advButton.getContentDescription()).isEqualTo(
                 mContext.getString(R.string.wifi_advanced_toggle_description));
     }
+
+    @Test
+    public void getVisibility_whenAdvancedOptionClicked_shouldBeGone() {
+        final CheckBox advButton = mView.findViewById(R.id.wifi_advanced_togglebox);
+
+        advButton.performClick();
+
+        assertThat(advButton.getVisibility()).isEqualTo(View.GONE);
+    }
 }