[Wi-Fi HotSpot] Improve Wi-Fi hotspot settings entries visibility problem

When the security type of hotspot changed, the hidden item will showed because of the Expanded child list is set as constant.

To improve it, dynamicall adjust the Expanded child count according to the security type.

Bug: 138594907
Test: Manually
      1. Enter Settings APP -> Network & internet -> Hotspot & tethering
      ->Wi-Fi hotspot
      2. Check if there are only two expanded items if the
      Security type is None, or three expaned items if the Security type
      is WPA2-personal
      3. Change the Security type and back to check item 2 match or not.

Change-Id: I84d1c5dca94d6a218cfc7ecd57e201e1cffdd878