Fix unexpected Wi-Fi hotspot shutdown

- Filter out unnecessary onSwitchChanged callbacks when the switch is
  disabled, which should not be triggered by user input.

- Refine the state handling function to avoid unnecessary
  onSwitchChanged callback.

- Refine the error handling of isHotspotPasswordValid function.

Bug: 227719584
Test: manual test
make RunSettingsRoboTests \
  ROBOTEST_FILTER=WifiTetherSwitchBarControllerTest

Change-Id: If62aaadc8ddb214769b1367d7801b6125bb5377c

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

@@ -72,7 +72,7 @@ public class WifiUtils extends com.android.settingslib.wifi.WifiUtils {
                 }
             }
             configBuilder.setPassphrase(password, securityType);
-        } catch (IllegalArgumentException e) {
+        } catch (Exception e) {
             return false;
         }
         return true;