Add an additional flag guard for Private Space implementation

This a layer of flag guarding only for the implementation of Private Space features excluding the APIs. The MVP flag allow_private_profile still guards all the features including the APIs.

Bug: 326060689
Test: Manual - a few verifications that some feeatures are unavailable when this flag is disabled
Test: Run presubmits and verify that nothing breaks
Change-Id: I05f7e2f20c6132b33484bb133ce03a933ece485f

src/com/android/settings/SettingsInitialize.java

@@ -118,7 +118,8 @@ public class SettingsInitialize extends BroadcastReceiver {
     }
 
     private void privateProfileSetup(Context context, PackageManager pm, UserInfo userInfo) {
-        if (Flags.allowPrivateProfile()) {
+        if (Flags.allowPrivateProfile()
+                && android.multiuser.Flags.enablePrivateSpaceFeatures()) {
             if (userInfo == null || !userInfo.isPrivateProfile()) {
                 return;
             }