Include a developer option sliding flag to toggle the different amount of apps to show

Bug: 299294792
Test: Verified SearchTransitionController didn't regress by turning off BACKGROUND_DRAWABLES flag.
Flag: ACONFIG com.android.launcher3.Flags.enable_private_space DEVELOPMENT
Change-Id: I78ee3a9dbc2d60f1b7acaa5834a8c656217a07d8

quickstep/src/com/android/launcher3/uioverrides/flags/DeveloperOptionsUI.java

@@ -28,6 +28,7 @@ import static com.android.launcher3.LauncherPrefs.LONG_PRESS_NAV_HANDLE_HAPTIC_H
 import static com.android.launcher3.LauncherPrefs.LONG_PRESS_NAV_HANDLE_HAPTIC_HINT_START_SCALE_PERCENT;
 import static com.android.launcher3.LauncherPrefs.LONG_PRESS_NAV_HANDLE_SLOP_PERCENTAGE;
 import static com.android.launcher3.LauncherPrefs.LONG_PRESS_NAV_HANDLE_TIMEOUT_MS;
+import static com.android.launcher3.LauncherPrefs.PRIVATE_SPACE_APPS;
 import static com.android.launcher3.settings.SettingsActivity.EXTRA_FRAGMENT_HIGHLIGHT_KEY;
 import static com.android.launcher3.uioverrides.plugins.PluginManagerWrapper.PLUGIN_CHANGED;
 import static com.android.launcher3.uioverrides.plugins.PluginManagerWrapper.pluginEnabledKey;
@@ -67,6 +68,7 @@ import androidx.preference.SeekBarPreference;
 import androidx.preference.SwitchPreference;
 
 import com.android.launcher3.ConstantItem;
+import com.android.launcher3.Flags;
 import com.android.launcher3.LauncherPrefs;
 import com.android.launcher3.R;
 import com.android.launcher3.config.FeatureFlags;
@@ -115,6 +117,9 @@ public class DeveloperOptionsUI {
             addAllAppsFromOverviewCatergory();
         }
         addCustomLpnhCategory();
+        if (Flags.enablePrivateSpace()) {
+            addCustomPrivateAppsCategory();
+        }
     }
 
     private void filterPreferences(String query, PreferenceGroup pg) {
@@ -365,6 +370,12 @@ public class DeveloperOptionsUI {
         }
     }
 
+    private void addCustomPrivateAppsCategory() {
+        PreferenceCategory category = newCategory("Apps in Private Space Config");
+        category.addPreference(createSeekBarPreference(
+                "Number of Apps to put in private region", 0, 100, 1, PRIVATE_SPACE_APPS));
+    }
+
     /**
      * Create a preference with text and a seek bar. Should be added to a PreferenceCategory.
      *