Disable PS entry point and Activity when PS is not allowed.

In this change we disable:
1. Security Center Entry point
2. PrivateSpaceAuthenticationActivity

when private profile is not present and cannot be added.

Additionally, the intent exposing PrivateSpaceAuthenticationActivity
is also non-exported and changed to a better name.

Bug: 328578044
Test: Manual build and flash
Change-Id: I13d298316c6d719d0b06e4969989ea1da83dd4c6

src/com/android/settings/privatespace/PrivateSpaceMaintainer.java

@@ -155,7 +155,7 @@ public class PrivateSpaceMaintainer {
             return true;
         }
 
-        List<UserInfo> users = mUserManager.getProfiles(0);
+        List<UserInfo> users = mUserManager.getProfiles(mContext.getUserId());
         for (UserInfo user : users) {
             if (user.isPrivateProfile()) {
                 mUserHandle = user.getUserHandle();