Make user explicitly set security type for tether network

This was made implicit which is confusing for the user so this CL
adds a preference to make the user manually choose their security
type.

Test: robotests
Bug: 79435112
Change-Id: Ie78806e8952b52e1b7cd21f0b87c9d064acaff64

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

@@ -50,7 +50,7 @@ public class WifiUtils {
 
     public static boolean isHotspotPasswordValid(String password) {
         if (TextUtils.isEmpty(password)) {
-            return true;
+            return false;
         }
 
         final int length = password.length();