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/privatespace/PrivateSpaceSetLockFragment.java

@@ -51,7 +51,8 @@ public class PrivateSpaceSetLockFragment extends InstrumentedFragment {
             LayoutInflater inflater,
             @Nullable ViewGroup container,
             @Nullable Bundle savedInstanceState) {
-        if (!android.os.Flags.allowPrivateProfile()) {
+        if (!android.os.Flags.allowPrivateProfile()
+                || !android.multiuser.Flags.enablePrivateSpaceFeatures()) {
             return null;
         }
         GlifLayout rootView =